Calculus Examples

$e^{- x} (x^{2} + 2 x)$

Step 1

Find the first derivative of the function.

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Step 1.1

Differentiate using the Product Rule which states that $\frac{d}{d x} [f (x) g (x)]$ is $f (x) \frac{d}{d x} [g (x)] + g (x) \frac{d}{d x} [f (x)]$ where $f (x) = e^{- x}$ and $g (x) = x^{2} + 2 x$ .

$e^{- x} \frac{d}{d x} [x^{2} + 2 x] + (x^{2} + 2 x) \frac{d}{d x} [e^{- x}]$

Step 1.2

Differentiate.

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Step 1.2.1

By the Sum Rule, the derivative of $x^{2} + 2 x$ with respect to $x$ is $\frac{d}{d x} [x^{2}] + \frac{d}{d x} [2 x]$ .

$e^{- x} (\frac{d}{d x} [x^{2}] + \frac{d}{d x} [2 x]) + (x^{2} + 2 x) \frac{d}{d x} [e^{- x}]$

Step 1.2.2

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 2$ .

$e^{- x} (2 x + \frac{d}{d x} [2 x]) + (x^{2} + 2 x) \frac{d}{d x} [e^{- x}]$

Step 1.2.3

Since $2$ is constant with respect to $x$ , the derivative of $2 x$ with respect to $x$ is $2 \frac{d}{d x} [x]$ .

$e^{- x} (2 x + 2 \frac{d}{d x} [x]) + (x^{2} + 2 x) \frac{d}{d x} [e^{- x}]$

Step 1.2.4

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 1$ .

$e^{- x} (2 x + 2 \cdot 1) + (x^{2} + 2 x) \frac{d}{d x} [e^{- x}]$

Step 1.2.5

Multiply $2$ by $1$ .

$e^{- x} (2 x + 2) + (x^{2} + 2 x) \frac{d}{d x} [e^{- x}]$

Step 1.3

Differentiate using the chain rule, which states that $\frac{d}{d x} [f (g (x))]$ is $f' (g (x)) g' (x)$ where $f (x) = e^{x}$ and $g (x) = - x$ .

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Step 1.3.1

To apply the Chain Rule, set $u$ as $- x$ .

$e^{- x} (2 x + 2) + (x^{2} + 2 x) (\frac{d}{d u} [e^{u}] \frac{d}{d x} [- x])$

Step 1.3.2

Differentiate using the Exponential Rule which states that $\frac{d}{d u} [a^{u}]$ is $a^{u} \ln (a)$ where $a$ = $e$ .

$e^{- x} (2 x + 2) + (x^{2} + 2 x) (e^{u} \frac{d}{d x} [- x])$

Step 1.3.3

Replace all occurrences of $u$ with $- x$ .

$e^{- x} (2 x + 2) + (x^{2} + 2 x) (e^{- x} \frac{d}{d x} [- x])$

Step 1.4

Differentiate.

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Step 1.4.1

Since $- 1$ is constant with respect to $x$ , the derivative of $- x$ with respect to $x$ is $- \frac{d}{d x} [x]$ .

$e^{- x} (2 x + 2) + (x^{2} + 2 x) e^{- x} (- \frac{d}{d x} [x])$

Step 1.4.2

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 1$ .

$e^{- x} (2 x + 2) + (x^{2} + 2 x) e^{- x} (- 1 \cdot 1)$

Step 1.4.3

Simplify the expression.

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Step 1.4.3.1

Multiply $- 1$ by $1$ .

$e^{- x} (2 x + 2) + (x^{2} + 2 x) e^{- x} \cdot - 1$

Step 1.4.3.2

Move $- 1$ to the left of $(x^{2} + 2 x) e^{- x}$ .

$e^{- x} (2 x + 2) - 1 \cdot ((x^{2} + 2 x) e^{- x})$

Step 1.4.3.3

Rewrite $- 1 (x^{2} + 2 x)$ as $- (x^{2} + 2 x)$ .

$e^{- x} (2 x + 2) - (x^{2} + 2 x) e^{- x}$

Step 1.5

Simplify.

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Step 1.5.1

Apply the distributive property.

$e^{- x} (2 x) + e^{- x} \cdot 2 - (x^{2} + 2 x) e^{- x}$

Step 1.5.2

Apply the distributive property.

$e^{- x} (2 x) + e^{- x} \cdot 2 + (- x^{2} - (2 x)) e^{- x}$

Step 1.5.3

Apply the distributive property.

$e^{- x} (2 x) + e^{- x} \cdot 2 - x^{2} e^{- x} - (2 x) e^{- x}$

Step 1.5.4

Combine terms.

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Step 1.5.4.1

Move $2$ to the left of $e^{- x}$ .

$e^{- x} (2 x) + 2 \cdot e^{- x} - x^{2} e^{- x} - (2 x) e^{- x}$

Step 1.5.4.2

Multiply $2$ by $- 1$ .

$e^{- x} (2 x) + 2 e^{- x} - x^{2} e^{- x} - 2 x e^{- x}$

Step 1.5.4.3

Subtract $2 x e^{- x}$ from $e^{- x} (2 x)$ .

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Step 1.5.4.3.1

Move $e^{- x}$ .

$2 e^{- x} - x^{2} e^{- x} + 2 x e^{- x} - 2 x e^{- x}$

Step 1.5.4.3.2

Subtract $2 x e^{- x}$ from $2 x e^{- x}$ .

$2 e^{- x} - x^{2} e^{- x} + 0$

Step 1.5.4.4

Add $2 e^{- x} - x^{2} e^{- x}$ and $0$ .

$2 e^{- x} - x^{2} e^{- x}$

Step 1.5.5

Reorder terms.

$- e^{- x} x^{2} + 2 e^{- x}$

Step 1.5.6

Reorder factors in $- e^{- x} x^{2} + 2 e^{- x}$ .

$- x^{2} e^{- x} + 2 e^{- x}$

Step 2

Find the second derivative of the function.

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Step 2.1

By the Sum Rule, the derivative of $- x^{2} e^{- x} + 2 e^{- x}$ with respect to $x$ is $\frac{d}{d x} [- x^{2} e^{- x}] + \frac{d}{d x} [2 e^{- x}]$ .

$f'' (x) = \frac{d}{d x} (- x^{2} e^{- x}) + \frac{d}{d x} (2 e^{- x})$

Step 2.2

Evaluate $\frac{d}{d x} [- x^{2} e^{- x}]$ .

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Step 2.2.1

Since $- 1$ is constant with respect to $x$ , the derivative of $- x^{2} e^{- x}$ with respect to $x$ is $- \frac{d}{d x} [x^{2} e^{- x}]$ .

$f'' (x) = - \frac{d}{d x} (x^{2} e^{- x}) + \frac{d}{d x} (2 e^{- x})$

Step 2.2.2

Differentiate using the Product Rule which states that $\frac{d}{d x} [f (x) g (x)]$ is $f (x) \frac{d}{d x} [g (x)] + g (x) \frac{d}{d x} [f (x)]$ where $f (x) = x^{2}$ and $g (x) = e^{- x}$ .

$f'' (x) = - (x^{2} \frac{d}{d x} (e^{- x}) + e^{- x} \frac{d}{d x} (x^{2})) + \frac{d}{d x} (2 e^{- x})$

Step 2.2.3

Differentiate using the chain rule, which states that $\frac{d}{d x} [f (g (x))]$ is $f' (g (x)) g' (x)$ where $f (x) = e^{x}$ and $g (x) = - x$ .

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Step 2.2.3.1

To apply the Chain Rule, set $u_{1}$ as $- x$ .

$f'' (x) = - (x^{2} (\frac{d}{d u (1)} (e^{u_{1}}) \frac{d}{d x} (- x)) + e^{- x} \frac{d}{d x} (x^{2})) + \frac{d}{d x} (2 e^{- x})$

Step 2.2.3.2

Differentiate using the Exponential Rule which states that $\frac{d}{d u_{1}} [a^{u_{1}}]$ is $a^{u_{1}} \ln (a)$ where $a$ = $e$ .

$f'' (x) = - (x^{2} (e^{u_{1}} \frac{d}{d x} (- x)) + e^{- x} \frac{d}{d x} (x^{2})) + \frac{d}{d x} (2 e^{- x})$

Step 2.2.3.3

Replace all occurrences of $u_{1}$ with $- x$ .

$f'' (x) = - (x^{2} (e^{- x} \frac{d}{d x} (- x)) + e^{- x} \frac{d}{d x} (x^{2})) + \frac{d}{d x} (2 e^{- x})$

Step 2.2.4

Since $- 1$ is constant with respect to $x$ , the derivative of $- x$ with respect to $x$ is $- \frac{d}{d x} [x]$ .

$f'' (x) = - (x^{2} (e^{- x} (- \frac{d}{d x} x)) + e^{- x} \frac{d}{d x} (x^{2})) + \frac{d}{d x} (2 e^{- x})$

Step 2.2.5

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 1$ .

$f'' (x) = - (x^{2} (e^{- x} (- 1 \cdot 1)) + e^{- x} \frac{d}{d x} (x^{2})) + \frac{d}{d x} (2 e^{- x})$

Step 2.2.6

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 2$ .

$f'' (x) = - (x^{2} (e^{- x} (- 1 \cdot 1)) + e^{- x} (2 x)) + \frac{d}{d x} (2 e^{- x})$

Step 2.2.7

Multiply $- 1$ by $1$ .

$f'' (x) = - (x^{2} (e^{- x} \cdot - 1) + e^{- x} (2 x)) + \frac{d}{d x} (2 e^{- x})$

Step 2.2.8

Move $- 1$ to the left of $e^{- x}$ .

$f'' (x) = - (x^{2} (- 1 \cdot e^{- x}) + e^{- x} (2 x)) + \frac{d}{d x} (2 e^{- x})$

Step 2.2.9

Rewrite $- 1 e^{- x}$ as $- e^{- x}$ .

$f'' (x) = - (x^{2} (- e^{- x}) + e^{- x} (2 x)) + \frac{d}{d x} (2 e^{- x})$

Step 2.3

Evaluate $\frac{d}{d x} [2 e^{- x}]$ .

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Step 2.3.1

Since $2$ is constant with respect to $x$ , the derivative of $2 e^{- x}$ with respect to $x$ is $2 \frac{d}{d x} [e^{- x}]$ .

$f'' (x) = - (x^{2} (- e^{- x}) + e^{- x} (2 x)) + 2 \frac{d}{d x} (e^{- x})$

Step 2.3.2

Differentiate using the chain rule, which states that $\frac{d}{d x} [f (g (x))]$ is $f' (g (x)) g' (x)$ where $f (x) = e^{x}$ and $g (x) = - x$ .

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Step 2.3.2.1

To apply the Chain Rule, set $u_{2}$ as $- x$ .

$f'' (x) = - (x^{2} (- e^{- x}) + e^{- x} (2 x)) + 2 (\frac{d}{d u (2)} (e^{u_{2}}) \frac{d}{d x} (- x))$

Step 2.3.2.2

Differentiate using the Exponential Rule which states that $\frac{d}{d u_{2}} [a^{u_{2}}]$ is $a^{u_{2}} \ln (a)$ where $a$ = $e$ .

$f'' (x) = - (x^{2} (- e^{- x}) + e^{- x} (2 x)) + 2 (e^{u_{2}} \frac{d}{d x} (- x))$

Step 2.3.2.3

Replace all occurrences of $u_{2}$ with $- x$ .

$f'' (x) = - (x^{2} (- e^{- x}) + e^{- x} (2 x)) + 2 (e^{- x} \frac{d}{d x} (- x))$

Step 2.3.3

Since $- 1$ is constant with respect to $x$ , the derivative of $- x$ with respect to $x$ is $- \frac{d}{d x} [x]$ .

$f'' (x) = - (x^{2} (- e^{- x}) + e^{- x} (2 x)) + 2 (e^{- x} (- \frac{d}{d x} x))$

Step 2.3.4

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 1$ .

$f'' (x) = - (x^{2} (- e^{- x}) + e^{- x} (2 x)) + 2 (e^{- x} (- 1 \cdot 1))$

Step 2.3.5

Multiply $- 1$ by $1$ .

$f'' (x) = - (x^{2} (- e^{- x}) + e^{- x} (2 x)) + 2 (e^{- x} \cdot - 1)$

Step 2.3.6

Move $- 1$ to the left of $e^{- x}$ .

$f'' (x) = - (x^{2} (- e^{- x}) + e^{- x} (2 x)) + 2 (- 1 \cdot e^{- x})$

Step 2.3.7

Rewrite $- 1 e^{- x}$ as $- e^{- x}$ .

$f'' (x) = - (x^{2} (- e^{- x}) + e^{- x} (2 x)) + 2 (- e^{- x})$

Step 2.3.8

Multiply $- 1$ by $2$ .

$f'' (x) = - (x^{2} (- e^{- x}) + e^{- x} (2 x)) - 2 e^{- x}$

Step 2.4

Simplify.

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Step 2.4.1

Apply the distributive property.

$f'' (x) = - (x^{2} (- e^{- x})) - (e^{- x} (2 x)) - 2 e^{- x}$

Step 2.4.2

Combine terms.

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Step 2.4.2.1

Multiply $- 1$ by $- 1$ .

$f'' (x) = 1 (x^{2} (e^{- x})) - (e^{- x} (2 x)) - 2 e^{- x}$

Step 2.4.2.2

Multiply $x^{2}$ by $1$ .

$f'' (x) = x^{2} e^{- x} - (e^{- x} (2 x)) - 2 e^{- x}$

Step 2.4.2.3

Multiply $2$ by $- 1$ .

$f'' (x) = x^{2} e^{- x} - 2 e^{- x} x - 2 e^{- x}$

Step 2.4.3

Reorder terms.

$f'' (x) = e^{- x} x^{2} - 2 e^{- x} x - 2 e^{- x}$

Step 2.4.4

Reorder factors in $e^{- x} x^{2} - 2 e^{- x} x - 2 e^{- x}$ .

$f'' (x) = x^{2} e^{- x} - 2 x e^{- x} - 2 e^{- x}$

Step 3

To find the local maximum and minimum values of the function, set the derivative equal to $0$ and solve.

$- x^{2} e^{- x} + 2 e^{- x} = 0$

Step 4

Find the first derivative.

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Step 4.1

Find the first derivative.

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Step 4.1.1

Differentiate using the Product Rule which states that $\frac{d}{d x} [f (x) g (x)]$ is $f (x) \frac{d}{d x} [g (x)] + g (x) \frac{d}{d x} [f (x)]$ where $f (x) = e^{- x}$ and $g (x) = x^{2} + 2 x$ .

$e^{- x} \frac{d}{d x} [x^{2} + 2 x] + (x^{2} + 2 x) \frac{d}{d x} [e^{- x}]$

Step 4.1.2

Differentiate.

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Step 4.1.2.1

By the Sum Rule, the derivative of $x^{2} + 2 x$ with respect to $x$ is $\frac{d}{d x} [x^{2}] + \frac{d}{d x} [2 x]$ .

$e^{- x} (\frac{d}{d x} [x^{2}] + \frac{d}{d x} [2 x]) + (x^{2} + 2 x) \frac{d}{d x} [e^{- x}]$

Step 4.1.2.2

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 2$ .

$e^{- x} (2 x + \frac{d}{d x} [2 x]) + (x^{2} + 2 x) \frac{d}{d x} [e^{- x}]$

Step 4.1.2.3

Since $2$ is constant with respect to $x$ , the derivative of $2 x$ with respect to $x$ is $2 \frac{d}{d x} [x]$ .

$e^{- x} (2 x + 2 \frac{d}{d x} [x]) + (x^{2} + 2 x) \frac{d}{d x} [e^{- x}]$

Step 4.1.2.4

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 1$ .

$e^{- x} (2 x + 2 \cdot 1) + (x^{2} + 2 x) \frac{d}{d x} [e^{- x}]$

Step 4.1.2.5

Multiply $2$ by $1$ .

$e^{- x} (2 x + 2) + (x^{2} + 2 x) \frac{d}{d x} [e^{- x}]$

Step 4.1.3

Differentiate using the chain rule, which states that $\frac{d}{d x} [f (g (x))]$ is $f' (g (x)) g' (x)$ where $f (x) = e^{x}$ and $g (x) = - x$ .

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Step 4.1.3.1

To apply the Chain Rule, set $u$ as $- x$ .

$e^{- x} (2 x + 2) + (x^{2} + 2 x) (\frac{d}{d u} [e^{u}] \frac{d}{d x} [- x])$

Step 4.1.3.2

Differentiate using the Exponential Rule which states that $\frac{d}{d u} [a^{u}]$ is $a^{u} \ln (a)$ where $a$ = $e$ .

$e^{- x} (2 x + 2) + (x^{2} + 2 x) (e^{u} \frac{d}{d x} [- x])$

Step 4.1.3.3

Replace all occurrences of $u$ with $- x$ .

$e^{- x} (2 x + 2) + (x^{2} + 2 x) (e^{- x} \frac{d}{d x} [- x])$

Step 4.1.4

Differentiate.

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Step 4.1.4.1

Since $- 1$ is constant with respect to $x$ , the derivative of $- x$ with respect to $x$ is $- \frac{d}{d x} [x]$ .

$e^{- x} (2 x + 2) + (x^{2} + 2 x) e^{- x} (- \frac{d}{d x} [x])$

Step 4.1.4.2

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 1$ .

$e^{- x} (2 x + 2) + (x^{2} + 2 x) e^{- x} (- 1 \cdot 1)$

Step 4.1.4.3

Simplify the expression.

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Step 4.1.4.3.1

Multiply $- 1$ by $1$ .

$e^{- x} (2 x + 2) + (x^{2} + 2 x) e^{- x} \cdot - 1$

Step 4.1.4.3.2

Move $- 1$ to the left of $(x^{2} + 2 x) e^{- x}$ .

$e^{- x} (2 x + 2) - 1 \cdot ((x^{2} + 2 x) e^{- x})$

Step 4.1.4.3.3

Rewrite $- 1 (x^{2} + 2 x)$ as $- (x^{2} + 2 x)$ .

$e^{- x} (2 x + 2) - (x^{2} + 2 x) e^{- x}$

Step 4.1.5

Simplify.

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Step 4.1.5.1

Apply the distributive property.

$e^{- x} (2 x) + e^{- x} \cdot 2 - (x^{2} + 2 x) e^{- x}$

Step 4.1.5.2

Apply the distributive property.

$e^{- x} (2 x) + e^{- x} \cdot 2 + (- x^{2} - (2 x)) e^{- x}$

Step 4.1.5.3

Apply the distributive property.

$e^{- x} (2 x) + e^{- x} \cdot 2 - x^{2} e^{- x} - (2 x) e^{- x}$

Step 4.1.5.4

Combine terms.

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Step 4.1.5.4.1

Move $2$ to the left of $e^{- x}$ .

$e^{- x} (2 x) + 2 \cdot e^{- x} - x^{2} e^{- x} - (2 x) e^{- x}$

Step 4.1.5.4.2

Multiply $2$ by $- 1$ .

$e^{- x} (2 x) + 2 e^{- x} - x^{2} e^{- x} - 2 x e^{- x}$

Step 4.1.5.4.3

Subtract $2 x e^{- x}$ from $e^{- x} (2 x)$ .

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Step 4.1.5.4.3.1

Move $e^{- x}$ .

$2 e^{- x} - x^{2} e^{- x} + 2 x e^{- x} - 2 x e^{- x}$

Step 4.1.5.4.3.2

Subtract $2 x e^{- x}$ from $2 x e^{- x}$ .

$2 e^{- x} - x^{2} e^{- x} + 0$

Step 4.1.5.4.4

Add $2 e^{- x} - x^{2} e^{- x}$ and $0$ .

$2 e^{- x} - x^{2} e^{- x}$

Step 4.1.5.5

Reorder terms.

$- e^{- x} x^{2} + 2 e^{- x}$

Step 4.1.5.6

Reorder factors in $- e^{- x} x^{2} + 2 e^{- x}$ .

$f' (x) = - x^{2} e^{- x} + 2 e^{- x}$

Step 4.2

The first derivative of $f (x)$ with respect to $x$ is $- x^{2} e^{- x} + 2 e^{- x}$ .

$- x^{2} e^{- x} + 2 e^{- x}$

Step 5

Set the first derivative equal to $0$ then solve the equation $- x^{2} e^{- x} + 2 e^{- x} = 0$ .

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Step 5.1

Set the first derivative equal to $0$ .

$- x^{2} e^{- x} + 2 e^{- x} = 0$

Step 5.2

Factor $e^{- x}$ out of $- x^{2} e^{- x} + 2 e^{- x}$ .

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Step 5.2.1

Factor $e^{- x}$ out of $- x^{2} e^{- x}$ .

$e^{- x} (- x^{2}) + 2 e^{- x} = 0$

Step 5.2.2

Factor $e^{- x}$ out of $2 e^{- x}$ .

$e^{- x} (- x^{2}) + e^{- x} \cdot 2 = 0$

Step 5.2.3

Factor $e^{- x}$ out of $e^{- x} (- x^{2}) + e^{- x} \cdot 2$ .

$e^{- x} (- x^{2} + 2) = 0$

Step 5.3

If any individual factor on the left side of the equation is equal to $0$ , the entire expression will be equal to $0$ .

$e^{- x} = 0$

$- x^{2} + 2 = 0$

Step 5.4

Set $e^{- x}$ equal to $0$ and solve for $x$ .

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Step 5.4.1

Set $e^{- x}$ equal to $0$ .

$e^{- x} = 0$

Step 5.4.2

Solve $e^{- x} = 0$ for $x$ .

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Step 5.4.2.1

Take the natural logarithm of both sides of the equation to remove the variable from the exponent.

$\ln (e^{- x}) = \ln (0)$

Step 5.4.2.2

The equation cannot be solved because $\ln (0)$ is undefined.

Undefined

Step 5.4.2.3

There is no solution for $e^{- x} = 0$

No solution

Step 5.5

Set $- x^{2} + 2$ equal to $0$ and solve for $x$ .

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Step 5.5.1

Set $- x^{2} + 2$ equal to $0$ .

$- x^{2} + 2 = 0$

Step 5.5.2

Solve $- x^{2} + 2 = 0$ for $x$ .

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Step 5.5.2.1

Subtract $2$ from both sides of the equation.

$- x^{2} = - 2$

Step 5.5.2.2

Divide each term in $- x^{2} = - 2$ by $- 1$ and simplify.

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Step 5.5.2.2.1

Divide each term in $- x^{2} = - 2$ by $- 1$ .

$\frac{- x^{2}}{- 1} = \frac{- 2}{- 1}$

Step 5.5.2.2.2

Simplify the left side.

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Step 5.5.2.2.2.1

Dividing two negative values results in a positive value.

$\frac{x^{2}}{1} = \frac{- 2}{- 1}$

Step 5.5.2.2.2.2

Divide $x^{2}$ by $1$ .

$x^{2} = \frac{- 2}{- 1}$

Step 5.5.2.2.3

Simplify the right side.

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Step 5.5.2.2.3.1

Divide $- 2$ by $- 1$ .

$x^{2} = 2$

Step 5.5.2.3

Take the specified root of both sides of the equation to eliminate the exponent on the left side.

$x = \pm \sqrt{2}$

Step 5.5.2.4

The complete solution is the result of both the positive and negative portions of the solution.

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Step 5.5.2.4.1

First, use the positive value of the $\pm$ to find the first solution.

$x = \sqrt{2}$

Step 5.5.2.4.2

Next, use the negative value of the $\pm$ to find the second solution.

$x = - \sqrt{2}$

Step 5.5.2.4.3

The complete solution is the result of both the positive and negative portions of the solution.

$x = \sqrt{2}, - \sqrt{2}$

Step 5.6

The final solution is all the values that make $e^{- x} (- x^{2} + 2) = 0$ true.

$x = \sqrt{2}, - \sqrt{2}$

Step 6

Find the values where the derivative is undefined.

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Step 6.1

The domain of the expression is all real numbers except where the expression is undefined. In this case, there is no real number that makes the expression undefined.

Step 7

Critical points to evaluate.

$x = \sqrt{2}, - \sqrt{2}$

Step 8

Evaluate the second derivative at $x = \sqrt{2}$ . If the second derivative is positive, then this is a local minimum. If it is negative, then this is a local maximum.

${(\sqrt{2})}^{2} e^{- (\sqrt{2})} - 2 \sqrt{2} e^{- (\sqrt{2})} - 2 e^{- (\sqrt{2})}$

Step 9

Evaluate the second derivative.

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Step 9.1

Rewrite ${\sqrt{2}}^{2}$ as $2$ .

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Step 9.1.1

Use $\sqrt[n]{a^{x}} = a^{\frac{x}{n}}$ to rewrite $\sqrt{2}$ as $2^{\frac{1}{2}}$ .

${(2^{\frac{1}{2}})}^{2} e^{- (\sqrt{2})} - 2 \sqrt{2} e^{- (\sqrt{2})} - 2 e^{- (\sqrt{2})}$

Step 9.1.2

Apply the power rule and multiply exponents, ${(a^{m})}^{n} = a^{m n}$ .

$2^{\frac{1}{2} \cdot 2} e^{- (\sqrt{2})} - 2 \sqrt{2} e^{- (\sqrt{2})} - 2 e^{- (\sqrt{2})}$

Step 9.1.3

Combine $\frac{1}{2}$ and $2$ .

$2^{\frac{2}{2}} e^{- (\sqrt{2})} - 2 \sqrt{2} e^{- (\sqrt{2})} - 2 e^{- (\sqrt{2})}$

Step 9.1.4

Cancel the common factor of $2$ .

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Step 9.1.4.1

Cancel the common factor.

$2^{\frac{2}{2}} e^{- (\sqrt{2})} - 2 \sqrt{2} e^{- (\sqrt{2})} - 2 e^{- (\sqrt{2})}$

Step 9.1.4.2

Rewrite the expression.

$2^{1} e^{- (\sqrt{2})} - 2 \sqrt{2} e^{- (\sqrt{2})} - 2 e^{- (\sqrt{2})}$

Step 9.1.5

Evaluate the exponent.

$2 e^{- (\sqrt{2})} - 2 \sqrt{2} e^{- (\sqrt{2})} - 2 e^{- (\sqrt{2})}$

$2 e^{- \sqrt{2}} - 2 \sqrt{2} e^{- \sqrt{2}} - 2 e^{- \sqrt{2}}$

Step 9.2

Simplify by adding terms.

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Step 9.2.1

Subtract $2 e^{- \sqrt{2}}$ from $2 e^{- \sqrt{2}}$ .

$- 2 \sqrt{2} e^{- \sqrt{2}} + 0$

Step 9.2.2

Add $- 2 \sqrt{2} e^{- \sqrt{2}}$ and $0$ .

$- 2 \sqrt{2} e^{- \sqrt{2}}$

Step 10

$x = \sqrt{2}$ is a local maximum because the value of the second derivative is negative. This is referred to as the second derivative test.

$x = \sqrt{2}$ is a local maximum

Step 11

Find the y-value when $x = \sqrt{2}$ .

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Step 11.1

Replace the variable $x$ with $\sqrt{2}$ in the expression.

$f (\sqrt{2}) = e^{- (\sqrt{2})} ({(\sqrt{2})}^{2} + 2 (\sqrt{2}))$

Step 11.2

Simplify the result.

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Step 11.2.1

Rewrite ${\sqrt{2}}^{2}$ as $2$ .

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Step 11.2.1.1

Use $\sqrt[n]{a^{x}} = a^{\frac{x}{n}}$ to rewrite $\sqrt{2}$ as $2^{\frac{1}{2}}$ .

$f (\sqrt{2}) = e^{- \sqrt{2}} ({(2^{\frac{1}{2}})}^{2} + 2 (\sqrt{2}))$

Step 11.2.1.2

Apply the power rule and multiply exponents, ${(a^{m})}^{n} = a^{m n}$ .

$f (\sqrt{2}) = e^{- \sqrt{2}} (2^{\frac{1}{2} \cdot 2} + 2 (\sqrt{2}))$

Step 11.2.1.3

Combine $\frac{1}{2}$ and $2$ .

$f (\sqrt{2}) = e^{- \sqrt{2}} (2^{\frac{2}{2}} + 2 (\sqrt{2}))$

Step 11.2.1.4

Cancel the common factor of $2$ .

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Step 11.2.1.4.1

Cancel the common factor.

$f (\sqrt{2}) = e^{- \sqrt{2}} (2^{\frac{2}{2}} + 2 (\sqrt{2}))$

Step 11.2.1.4.2

Rewrite the expression.

$f (\sqrt{2}) = e^{- \sqrt{2}} (2 + 2 (\sqrt{2}))$

Step 11.2.1.5

Evaluate the exponent.

$f (\sqrt{2}) = e^{- \sqrt{2}} (2 + 2 (\sqrt{2}))$

$f (\sqrt{2}) = e^{- \sqrt{2}} (2 + 2 \sqrt{2})$

Step 11.2.2

Simplify by multiplying through.

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Step 11.2.2.1

Apply the distributive property.

$f (\sqrt{2}) = e^{- \sqrt{2}} \cdot 2 + e^{- \sqrt{2}} (2 \sqrt{2})$

Step 11.2.2.2

Move $2$ to the left of $e^{- \sqrt{2}}$ .

$f (\sqrt{2}) = 2 \cdot e^{- \sqrt{2}} + e^{- \sqrt{2}} (2 \sqrt{2})$

Step 11.2.3

Move $2$ to the left of $e^{- \sqrt{2}}$ .

$f (\sqrt{2}) = 2 e^{- \sqrt{2}} + 2 e^{- \sqrt{2}} \sqrt{2}$

Step 11.2.4

The final answer is $2 e^{- \sqrt{2}} + 2 e^{- \sqrt{2}} \sqrt{2}$ .

$y = 2 e^{- \sqrt{2}} + 2 e^{- \sqrt{2}} \sqrt{2}$

Step 12

Evaluate the second derivative at $x = - \sqrt{2}$ . If the second derivative is positive, then this is a local minimum. If it is negative, then this is a local maximum.

${(- \sqrt{2})}^{2} e^{- (- \sqrt{2})} - 2 (- \sqrt{2}) e^{- (- \sqrt{2})} - 2 e^{- (- \sqrt{2})}$

Step 13

Evaluate the second derivative.

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Step 13.1

Simplify each term.

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Step 13.1.1

Apply the product rule to $- \sqrt{2}$ .

${(- 1)}^{2} {\sqrt{2}}^{2} e^{- (- \sqrt{2})} - 2 (- \sqrt{2}) e^{- (- \sqrt{2})} - 2 e^{- (- \sqrt{2})}$

Step 13.1.2

Raise $- 1$ to the power of $2$ .

$1 {\sqrt{2}}^{2} e^{- (- \sqrt{2})} - 2 (- \sqrt{2}) e^{- (- \sqrt{2})} - 2 e^{- (- \sqrt{2})}$

Step 13.1.3

Multiply ${\sqrt{2}}^{2}$ by $1$ .

${\sqrt{2}}^{2} e^{- (- \sqrt{2})} - 2 (- \sqrt{2}) e^{- (- \sqrt{2})} - 2 e^{- (- \sqrt{2})}$

Step 13.1.4

Rewrite ${\sqrt{2}}^{2}$ as $2$ .

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Step 13.1.4.1

Use $\sqrt[n]{a^{x}} = a^{\frac{x}{n}}$ to rewrite $\sqrt{2}$ as $2^{\frac{1}{2}}$ .

${(2^{\frac{1}{2}})}^{2} e^{- (- \sqrt{2})} - 2 (- \sqrt{2}) e^{- (- \sqrt{2})} - 2 e^{- (- \sqrt{2})}$

Step 13.1.4.2

Apply the power rule and multiply exponents, ${(a^{m})}^{n} = a^{m n}$ .

$2^{\frac{1}{2} \cdot 2} e^{- (- \sqrt{2})} - 2 (- \sqrt{2}) e^{- (- \sqrt{2})} - 2 e^{- (- \sqrt{2})}$

Step 13.1.4.3

Combine $\frac{1}{2}$ and $2$ .

$2^{\frac{2}{2}} e^{- (- \sqrt{2})} - 2 (- \sqrt{2}) e^{- (- \sqrt{2})} - 2 e^{- (- \sqrt{2})}$

Step 13.1.4.4

Cancel the common factor of $2$ .

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Step 13.1.4.4.1

Cancel the common factor.

$2^{\frac{2}{2}} e^{- (- \sqrt{2})} - 2 (- \sqrt{2}) e^{- (- \sqrt{2})} - 2 e^{- (- \sqrt{2})}$

Step 13.1.4.4.2

Rewrite the expression.

$2^{1} e^{- (- \sqrt{2})} - 2 (- \sqrt{2}) e^{- (- \sqrt{2})} - 2 e^{- (- \sqrt{2})}$

Step 13.1.4.5

Evaluate the exponent.

$2 e^{- (- \sqrt{2})} - 2 (- \sqrt{2}) e^{- (- \sqrt{2})} - 2 e^{- (- \sqrt{2})}$

Step 13.1.5

Multiply $- (- \sqrt{2})$ .

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Step 13.1.5.1

Multiply $- 1$ by $- 1$ .

$2 e^{1 \sqrt{2}} - 2 (- \sqrt{2}) e^{- (- \sqrt{2})} - 2 e^{- (- \sqrt{2})}$

Step 13.1.5.2

Multiply $\sqrt{2}$ by $1$ .

$2 e^{\sqrt{2}} - 2 (- \sqrt{2}) e^{- (- \sqrt{2})} - 2 e^{- (- \sqrt{2})}$

Step 13.1.6

Multiply $- 1$ by $- 2$ .

$2 e^{\sqrt{2}} + 2 \sqrt{2} e^{- (- \sqrt{2})} - 2 e^{- (- \sqrt{2})}$

Step 13.1.7

Multiply $- (- \sqrt{2})$ .

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Step 13.1.7.1

Multiply $- 1$ by $- 1$ .

$2 e^{\sqrt{2}} + 2 \sqrt{2} e^{1 \sqrt{2}} - 2 e^{- (- \sqrt{2})}$

Step 13.1.7.2

Multiply $\sqrt{2}$ by $1$ .

$2 e^{\sqrt{2}} + 2 \sqrt{2} e^{\sqrt{2}} - 2 e^{- (- \sqrt{2})}$

Step 13.1.8

Multiply $- (- \sqrt{2})$ .

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Step 13.1.8.1

Multiply $- 1$ by $- 1$ .

$2 e^{\sqrt{2}} + 2 \sqrt{2} e^{\sqrt{2}} - 2 e^{1 \sqrt{2}}$

Step 13.1.8.2

Multiply $\sqrt{2}$ by $1$ .

$2 e^{\sqrt{2}} + 2 \sqrt{2} e^{\sqrt{2}} - 2 e^{\sqrt{2}}$

Step 13.2

Simplify by adding terms.

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Step 13.2.1

Subtract $2 e^{\sqrt{2}}$ from $2 e^{\sqrt{2}}$ .

$2 \sqrt{2} e^{\sqrt{2}} + 0$

Step 13.2.2

Add $2 \sqrt{2} e^{\sqrt{2}}$ and $0$ .

$2 \sqrt{2} e^{\sqrt{2}}$

Step 14

$x = - \sqrt{2}$ is a local minimum because the value of the second derivative is positive. This is referred to as the second derivative test.

$x = - \sqrt{2}$ is a local minimum

Step 15

Find the y-value when $x = - \sqrt{2}$ .

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Step 15.1

Replace the variable $x$ with $- \sqrt{2}$ in the expression.

$f (- \sqrt{2}) = e^{- (- \sqrt{2})} ({(- \sqrt{2})}^{2} + 2 (- \sqrt{2}))$

Step 15.2

Simplify the result.

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Step 15.2.1

Multiply $- (- \sqrt{2})$ .

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Step 15.2.1.1

Multiply $- 1$ by $- 1$ .

$f (- \sqrt{2}) = e^{1 \sqrt{2}} ({(- \sqrt{2})}^{2} + 2 (- \sqrt{2}))$

Step 15.2.1.2

Multiply $\sqrt{2}$ by $1$ .

$f (- \sqrt{2}) = e^{\sqrt{2}} ({(- \sqrt{2})}^{2} + 2 (- \sqrt{2}))$

Step 15.2.2

Simplify each term.

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Step 15.2.2.1

Apply the product rule to $- \sqrt{2}$ .

$f (- \sqrt{2}) = e^{\sqrt{2}} ({(- 1)}^{2} {\sqrt{2}}^{2} + 2 (- \sqrt{2}))$

Step 15.2.2.2

Raise $- 1$ to the power of $2$ .

$f (- \sqrt{2}) = e^{\sqrt{2}} (1 {\sqrt{2}}^{2} + 2 (- \sqrt{2}))$

Step 15.2.2.3

Multiply ${\sqrt{2}}^{2}$ by $1$ .

$f (- \sqrt{2}) = e^{\sqrt{2}} ({\sqrt{2}}^{2} + 2 (- \sqrt{2}))$

Step 15.2.2.4

Rewrite ${\sqrt{2}}^{2}$ as $2$ .

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Step 15.2.2.4.1

Use $\sqrt[n]{a^{x}} = a^{\frac{x}{n}}$ to rewrite $\sqrt{2}$ as $2^{\frac{1}{2}}$ .

$f (- \sqrt{2}) = e^{\sqrt{2}} ({(2^{\frac{1}{2}})}^{2} + 2 (- \sqrt{2}))$

Step 15.2.2.4.2

Apply the power rule and multiply exponents, ${(a^{m})}^{n} = a^{m n}$ .

$f (- \sqrt{2}) = e^{\sqrt{2}} (2^{\frac{1}{2} \cdot 2} + 2 (- \sqrt{2}))$

Step 15.2.2.4.3

Combine $\frac{1}{2}$ and $2$ .

$f (- \sqrt{2}) = e^{\sqrt{2}} (2^{\frac{2}{2}} + 2 (- \sqrt{2}))$

Step 15.2.2.4.4

Cancel the common factor of $2$ .

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Step 15.2.2.4.4.1

Cancel the common factor.

$f (- \sqrt{2}) = e^{\sqrt{2}} (2^{\frac{2}{2}} + 2 (- \sqrt{2}))$

Step 15.2.2.4.4.2

Rewrite the expression.

$f (- \sqrt{2}) = e^{\sqrt{2}} (2 + 2 (- \sqrt{2}))$

Step 15.2.2.4.5

Evaluate the exponent.

$f (- \sqrt{2}) = e^{\sqrt{2}} (2 + 2 (- \sqrt{2}))$

Step 15.2.2.5

Multiply $- 1$ by $2$ .

$f (- \sqrt{2}) = e^{\sqrt{2}} (2 - 2 \sqrt{2})$

Step 15.2.3

Simplify by multiplying through.

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Step 15.2.3.1

Apply the distributive property.

$f (- \sqrt{2}) = e^{\sqrt{2}} \cdot 2 + e^{\sqrt{2}} (- 2 \sqrt{2})$

Step 15.2.3.2

Move $2$ to the left of $e^{\sqrt{2}}$ .

$f (- \sqrt{2}) = 2 e^{\sqrt{2}} + e^{\sqrt{2}} (- 2 \sqrt{2})$

Step 15.2.4

The final answer is $2 e^{\sqrt{2}} + e^{\sqrt{2}} (- 2 \sqrt{2})$ .

$y = 2 e^{\sqrt{2}} + e^{\sqrt{2}} (- 2 \sqrt{2})$

Step 16

These are the local extrema for $f (x) = e^{- x} (x^{2} + 2 x)$ .

$(\sqrt{2}, 2 e^{- \sqrt{2}} + 2 e^{- \sqrt{2}} \sqrt{2})$ is a local maxima

$(- \sqrt{2}, 2 e^{\sqrt{2}} + e^{\sqrt{2}} (- 2 \sqrt{2}))$ is a local minima

Step 17