Calculus Examples

$y = {(x^{3} + 1)}^{x e^{x}}$

Step 1

Let $y = f (x)$ , take the natural logarithm of both sides $\ln (y) = \ln (f (x))$ .

$\ln (y) = \ln ({(x^{3} + 1)}^{x e^{x}})$

Step 2

Expand $\ln ({(x^{3} + 1)}^{x e^{x}})$ by moving $x e^{x}$ outside the logarithm.

$\ln (y) = x e^{x} \ln (x^{3} + 1)$

Step 3

Differentiate the expression using the chain rule, keeping in mind that $y$ is a function of $x$ .

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Step 3.1

Differentiate the left hand side $\ln (y)$ using the chain rule.

$\frac{y'}{y} = x e^{x} \ln (x^{3} + 1)$

Step 3.2

Differentiate the right hand side.

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Step 3.2.1

Differentiate $x e^{x} \ln (x^{3} + 1)$ .

$\frac{y'}{y} = \frac{d}{d x} [x e^{x} \ln (x^{3} + 1)]$

Step 3.2.2

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 $f (x) = x e^{x}$ and $g (x) = \ln (x^{3} + 1)$ .

$\frac{y'}{y} = x e^{x} \frac{d}{d x} [\ln (x^{3} + 1)] + \ln (x^{3} + 1) \frac{d}{d x} [x e^{x}]$

Step 3.2.3

Differentiate using the chain rule, which states that $\frac{d}{d x} [f (g (x))]$ is $f' (g (x)) g' (x)$ where $f (x) = \ln (x)$ and $g (x) = x^{3} + 1$ .

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Step 3.2.3.1

To apply the Chain Rule, set $u$ as $x^{3} + 1$ .

$\frac{y'}{y} = x e^{x} (\frac{d}{d u} [\ln (u)] \frac{d}{d x} [x^{3} + 1]) + \ln (x^{3} + 1) \frac{d}{d x} [x e^{x}]$

Step 3.2.3.2

The derivative of $\ln (u)$ with respect to $u$ is $\frac{1}{u}$ .

$\frac{y'}{y} = x e^{x} (\frac{1}{u} \frac{d}{d x} [x^{3} + 1]) + \ln (x^{3} + 1) \frac{d}{d x} [x e^{x}]$

Step 3.2.3.3

Replace all occurrences of $u$ with $x^{3} + 1$ .

$\frac{y'}{y} = x e^{x} (\frac{1}{x^{3} + 1} \frac{d}{d x} [x^{3} + 1]) + \ln (x^{3} + 1) \frac{d}{d x} [x e^{x}]$

Step 3.2.4

Differentiate.

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Step 3.2.4.1

Combine $\frac{1}{x^{3} + 1}$ and $x$ .

$\frac{y'}{y} = \frac{x}{x^{3} + 1} e^{x} \frac{d}{d x} [x^{3} + 1] + \ln (x^{3} + 1) \frac{d}{d x} [x e^{x}]$

Step 3.2.4.2

Combine $\frac{x}{x^{3} + 1}$ and $e^{x}$ .

$\frac{y'}{y} = \frac{x e^{x}}{x^{3} + 1} \frac{d}{d x} [x^{3} + 1] + \ln (x^{3} + 1) \frac{d}{d x} [x e^{x}]$

Step 3.2.4.3

By the Sum Rule, the derivative of $x^{3} + 1$ with respect to $x$ is $\frac{d}{d x} [x^{3}] + \frac{d}{d x} [1]$ .

$\frac{y'}{y} = \frac{x e^{x}}{x^{3} + 1} (\frac{d}{d x} [x^{3}] + \frac{d}{d x} [1]) + \ln (x^{3} + 1) \frac{d}{d x} [x e^{x}]$

Step 3.2.4.4

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 3$ .

$\frac{y'}{y} = \frac{x e^{x}}{x^{3} + 1} (3 x^{2} + \frac{d}{d x} [1]) + \ln (x^{3} + 1) \frac{d}{d x} [x e^{x}]$

Step 3.2.4.5

Since $1$ is constant with respect to $x$ , the derivative of $1$ with respect to $x$ is $0$ .

$\frac{y'}{y} = \frac{x e^{x}}{x^{3} + 1} (3 x^{2} + 0) + \ln (x^{3} + 1) \frac{d}{d x} [x e^{x}]$

Step 3.2.4.6

Combine fractions.

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Step 3.2.4.6.1

Add $3 x^{2}$ and $0$ .

$\frac{y'}{y} = \frac{x e^{x}}{x^{3} + 1} (3 x^{2}) + \ln (x^{3} + 1) \frac{d}{d x} [x e^{x}]$

Step 3.2.4.6.2

Combine $3$ and $\frac{x e^{x}}{x^{3} + 1}$ .

$\frac{y'}{y} = \frac{3 (x e^{x})}{x^{3} + 1} x^{2} + \ln (x^{3} + 1) \frac{d}{d x} [x e^{x}]$

Step 3.2.4.6.3

Combine $\frac{3 (x e^{x})}{x^{3} + 1}$ and $x^{2}$ .

$\frac{y'}{y} = \frac{3 (x e^{x}) x^{2}}{x^{3} + 1} + \ln (x^{3} + 1) \frac{d}{d x} [x e^{x}]$

Step 3.2.5

Multiply $x$ by $x^{2}$ by adding the exponents.

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Step 3.2.5.1

Move $x^{2}$ .

$\frac{y'}{y} = \frac{3 (x^{2} x e^{x})}{x^{3} + 1} + \ln (x^{3} + 1) \frac{d}{d x} [x e^{x}]$

Step 3.2.5.2

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

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Step 3.2.5.2.1

Raise $x$ to the power of $1$ .

$\frac{y'}{y} = \frac{3 (x^{2} x^{1} e^{x})}{x^{3} + 1} + \ln (x^{3} + 1) \frac{d}{d x} [x e^{x}]$

Step 3.2.5.2.2

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

$\frac{y'}{y} = \frac{3 (x^{2 + 1} e^{x})}{x^{3} + 1} + \ln (x^{3} + 1) \frac{d}{d x} [x e^{x}]$

Step 3.2.5.3

Add $2$ and $1$ .

$\frac{y'}{y} = \frac{3 (x^{3} e^{x})}{x^{3} + 1} + \ln (x^{3} + 1) \frac{d}{d x} [x e^{x}]$

Step 3.2.6

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 $f (x) = x$ and $g (x) = e^{x}$ .

$\frac{y'}{y} = \frac{3 x^{3} e^{x}}{x^{3} + 1} + \ln (x^{3} + 1) (x \frac{d}{d x} [e^{x}] + e^{x} \frac{d}{d x} [x])$

Step 3.2.7

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

$\frac{y'}{y} = \frac{3 x^{3} e^{x}}{x^{3} + 1} + \ln (x^{3} + 1) (x e^{x} + e^{x} \frac{d}{d x} [x])$

Step 3.2.8

Differentiate using the Power Rule.

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Step 3.2.8.1

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

$\frac{y'}{y} = \frac{3 x^{3} e^{x}}{x^{3} + 1} + \ln (x^{3} + 1) (x e^{x} + e^{x} \cdot 1)$

Step 3.2.8.2

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

$\frac{y'}{y} = \frac{3 x^{3} e^{x}}{x^{3} + 1} + \ln (x^{3} + 1) (x e^{x} + e^{x})$

Step 3.2.9

To write $\ln (x^{3} + 1) (x e^{x} + e^{x})$ as a fraction with a common denominator, multiply by $\frac{x^{3} + 1}{x^{3} + 1}$ .

$\frac{y'}{y} = \frac{3 x^{3} e^{x}}{x^{3} + 1} + \frac{\ln (x^{3} + 1) (x e^{x} + e^{x}) (x^{3} + 1)}{x^{3} + 1}$

Step 3.2.10

Combine the numerators over the common denominator.

$\frac{y'}{y} = \frac{3 x^{3} e^{x} + \ln (x^{3} + 1) (x e^{x} + e^{x}) (x^{3} + 1)}{x^{3} + 1}$

Step 3.2.11

Simplify.

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Step 3.2.11.1

Simplify the numerator.

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Step 3.2.11.1.1

Simplify each term.

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Step 3.2.11.1.1.1

Apply the distributive property.

$\frac{y'}{y} = \frac{3 x^{3} e^{x} + (\ln (x^{3} + 1) (x e^{x}) + \ln (x^{3} + 1) e^{x}) (x^{3} + 1)}{x^{3} + 1}$

Step 3.2.11.1.1.2

Expand $(\ln (x^{3} + 1) (x e^{x}) + \ln (x^{3} + 1) e^{x}) (x^{3} + 1)$ using the FOIL Method.

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Step 3.2.11.1.1.2.1

Apply the distributive property.

$\frac{y'}{y} = \frac{3 x^{3} e^{x} + \ln (x^{3} + 1) (x e^{x}) (x^{3} + 1) + \ln (x^{3} + 1) e^{x} (x^{3} + 1)}{x^{3} + 1}$

Step 3.2.11.1.1.2.2

Apply the distributive property.

$\frac{y'}{y} = \frac{3 x^{3} e^{x} + \ln (x^{3} + 1) (x e^{x}) x^{3} + \ln (x^{3} + 1) (x e^{x}) \cdot 1 + \ln (x^{3} + 1) e^{x} (x^{3} + 1)}{x^{3} + 1}$

Step 3.2.11.1.1.2.3

Apply the distributive property.

$\frac{y'}{y} = \frac{3 x^{3} e^{x} + \ln (x^{3} + 1) (x e^{x}) x^{3} + \ln (x^{3} + 1) (x e^{x}) \cdot 1 + \ln (x^{3} + 1) e^{x} x^{3} + \ln (x^{3} + 1) e^{x} \cdot 1}{x^{3} + 1}$

Step 3.2.11.1.1.3

Simplify each term.

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Step 3.2.11.1.1.3.1

Multiply $x$ by $x^{3}$ by adding the exponents.

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Step 3.2.11.1.1.3.1.1

Move $x^{3}$ .

$\frac{y'}{y} = \frac{3 x^{3} e^{x} + \ln (x^{3} + 1) (x^{3} x e^{x}) + \ln (x^{3} + 1) (x e^{x}) \cdot 1 + \ln (x^{3} + 1) e^{x} x^{3} + \ln (x^{3} + 1) e^{x} \cdot 1}{x^{3} + 1}$

Step 3.2.11.1.1.3.1.2

Multiply $x^{3}$ by $x$ .

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Step 3.2.11.1.1.3.1.2.1

Raise $x$ to the power of $1$ .

$\frac{y'}{y} = \frac{3 x^{3} e^{x} + \ln (x^{3} + 1) (x^{3} x^{1} e^{x}) + \ln (x^{3} + 1) (x e^{x}) \cdot 1 + \ln (x^{3} + 1) e^{x} x^{3} + \ln (x^{3} + 1) e^{x} \cdot 1}{x^{3} + 1}$

Step 3.2.11.1.1.3.1.2.2

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

$\frac{y'}{y} = \frac{3 x^{3} e^{x} + \ln (x^{3} + 1) (x^{3 + 1} e^{x}) + \ln (x^{3} + 1) (x e^{x}) \cdot 1 + \ln (x^{3} + 1) e^{x} x^{3} + \ln (x^{3} + 1) e^{x} \cdot 1}{x^{3} + 1}$

Step 3.2.11.1.1.3.1.3

Add $3$ and $1$ .

$\frac{y'}{y} = \frac{3 x^{3} e^{x} + \ln (x^{3} + 1) (x^{4} e^{x}) + \ln (x^{3} + 1) (x e^{x}) \cdot 1 + \ln (x^{3} + 1) e^{x} x^{3} + \ln (x^{3} + 1) e^{x} \cdot 1}{x^{3} + 1}$

Step 3.2.11.1.1.3.2

Multiply $\ln (x^{3} + 1)$ by $1$ .

$\frac{y'}{y} = \frac{3 x^{3} e^{x} + \ln (x^{3} + 1) (x^{4} e^{x}) + x e^{x} \cdot \ln (x^{3} + 1) + \ln (x^{3} + 1) e^{x} x^{3} + \ln (x^{3} + 1) e^{x} \cdot 1}{x^{3} + 1}$

Step 3.2.11.1.1.3.3

Multiply $\ln (x^{3} + 1)$ by $1$ .

$\frac{y'}{y} = \frac{3 x^{3} e^{x} + \ln (x^{3} + 1) (x^{4} e^{x}) + x e^{x} \ln (x^{3} + 1) + \ln (x^{3} + 1) e^{x} x^{3} + \ln (x^{3} + 1) e^{x}}{x^{3} + 1}$

Step 3.2.11.1.2

Reorder factors in $3 x^{3} e^{x} + \ln (x^{3} + 1) (x^{4} e^{x}) + x e^{x} \ln (x^{3} + 1) + \ln (x^{3} + 1) e^{x} x^{3} + \ln (x^{3} + 1) e^{x}$ .

$\frac{y'}{y} = \frac{3 x^{3} e^{x} + x^{4} e^{x} \ln (x^{3} + 1) + x e^{x} \ln (x^{3} + 1) + x^{3} e^{x} \ln (x^{3} + 1) + e^{x} \ln (x^{3} + 1)}{x^{3} + 1}$

Step 3.2.11.2

Reorder terms.

$\frac{y'}{y} = \frac{3 e^{x} x^{3} + e^{x} x^{4} \ln (x^{3} + 1) + e^{x} x \ln (x^{3} + 1) + e^{x} x^{3} \ln (x^{3} + 1) + e^{x} \ln (x^{3} + 1)}{x^{3} + 1}$

Step 4

Isolate $y'$ and substitute the original function for $y$ in the right hand side.

$y' = \frac{3 e^{x} x^{3} + e^{x} x^{4} \ln (x^{3} + 1) + e^{x} x \ln (x^{3} + 1) + e^{x} x^{3} \ln (x^{3} + 1) + e^{x} \ln (x^{3} + 1)}{x^{3} + 1} {(x^{3} + 1)}^{x e^{x}}$

Step 5

Simplify the right hand side.

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Step 5.1

Simplify the denominator.

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Step 5.1.1

Rewrite $1$ as $1^{3}$ .

$y' = \frac{3 e^{x} x^{3} + e^{x} x^{4} \ln (x^{3} + 1) + e^{x} x \ln (x^{3} + 1) + e^{x} x^{3} \ln (x^{3} + 1) + e^{x} \ln (x^{3} + 1)}{x^{3} + 1^{3}} {(x^{3} + 1)}^{x e^{x}}$

Step 5.1.2

Since both terms are perfect cubes, factor using the sum of cubes formula, $a^{3} + b^{3} = (a + b) (a^{2} - a b + b^{2})$ where $a = x$ and $b = 1$ .

$y' = \frac{3 e^{x} x^{3} + e^{x} x^{4} \ln (x^{3} + 1) + e^{x} x \ln (x^{3} + 1) + e^{x} x^{3} \ln (x^{3} + 1) + e^{x} \ln (x^{3} + 1)}{(x + 1) (x^{2} - x \cdot 1 + 1^{2})} {(x^{3} + 1)}^{x e^{x}}$

Step 5.1.3

Simplify.

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Step 5.1.3.1

Multiply $- 1$ by $1$ .

$y' = \frac{3 e^{x} x^{3} + e^{x} x^{4} \ln (x^{3} + 1) + e^{x} x \ln (x^{3} + 1) + e^{x} x^{3} \ln (x^{3} + 1) + e^{x} \ln (x^{3} + 1)}{(x + 1) (x^{2} - x + 1^{2})} {(x^{3} + 1)}^{x e^{x}}$

Step 5.1.3.2

One to any power is one.

$y' = \frac{3 e^{x} x^{3} + e^{x} x^{4} \ln (x^{3} + 1) + e^{x} x \ln (x^{3} + 1) + e^{x} x^{3} \ln (x^{3} + 1) + e^{x} \ln (x^{3} + 1)}{(x + 1) (x^{2} - x + 1)} {(x^{3} + 1)}^{x e^{x}}$

Step 5.2

Combine $\frac{3 e^{x} x^{3} + e^{x} x^{4} \ln (x^{3} + 1) + e^{x} x \ln (x^{3} + 1) + e^{x} x^{3} \ln (x^{3} + 1) + e^{x} \ln (x^{3} + 1)}{(x + 1) (x^{2} - x + 1)}$ and ${(x^{3} + 1)}^{x e^{x}}$ .

$y' = \frac{(3 e^{x} x^{3} + e^{x} x^{4} \ln (x^{3} + 1) + e^{x} x \ln (x^{3} + 1) + e^{x} x^{3} \ln (x^{3} + 1) + e^{x} \ln (x^{3} + 1)) {(x^{3} + 1)}^{x e^{x}}}{(x + 1) (x^{2} - x + 1)}$

Step 5.3

Reorder factors in $\frac{(3 e^{x} x^{3} + e^{x} x^{4} \ln (x^{3} + 1) + e^{x} x \ln (x^{3} + 1) + e^{x} x^{3} \ln (x^{3} + 1) + e^{x} \ln (x^{3} + 1)) {(x^{3} + 1)}^{x e^{x}}}{(x + 1) (x^{2} - x + 1)}$ .

$y' = \frac{{(x^{3} + 1)}^{x e^{x}} (3 x^{3} e^{x} + x^{4} e^{x} \ln (x^{3} + 1) + x e^{x} \ln (x^{3} + 1) + x^{3} e^{x} \ln (x^{3} + 1) + e^{x} \ln (x^{3} + 1))}{(x + 1) (x^{2} - x + 1)}$