Calculus Examples

$y = x^{4} + 2 x^{2} + 8 x + 3$

Step 1

Find the first derivative of the function.

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Step 1.1

Differentiate.

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Step 1.1.1

By the Sum Rule, the derivative of $x^{4} + 2 x^{2} + 8 x + 3$ with respect to $x$ is $\frac{d}{d x} [x^{4}] + \frac{d}{d x} [2 x^{2}] + \frac{d}{d x} [8 x] + \frac{d}{d x} [3]$ .

$\frac{d}{d x} [x^{4}] + \frac{d}{d x} [2 x^{2}] + \frac{d}{d x} [8 x] + \frac{d}{d x} [3]$

Step 1.1.2

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 4$ .

$4 x^{3} + \frac{d}{d x} [2 x^{2}] + \frac{d}{d x} [8 x] + \frac{d}{d x} [3]$

Step 1.2

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

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Step 1.2.1

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

$4 x^{3} + 2 \frac{d}{d x} [x^{2}] + \frac{d}{d x} [8 x] + \frac{d}{d x} [3]$

Step 1.2.2

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

$4 x^{3} + 2 (2 x) + \frac{d}{d x} [8 x] + \frac{d}{d x} [3]$

Step 1.2.3

Multiply $2$ by $2$ .

$4 x^{3} + 4 x + \frac{d}{d x} [8 x] + \frac{d}{d x} [3]$

Step 1.3

Evaluate $\frac{d}{d x} [8 x]$ .

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Step 1.3.1

Since $8$ is constant with respect to $x$ , the derivative of $8 x$ with respect to $x$ is $8 \frac{d}{d x} [x]$ .

$4 x^{3} + 4 x + 8 \frac{d}{d x} [x] + \frac{d}{d x} [3]$

Step 1.3.2

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

$4 x^{3} + 4 x + 8 \cdot 1 + \frac{d}{d x} [3]$

Step 1.3.3

Multiply $8$ by $1$ .

$4 x^{3} + 4 x + 8 + \frac{d}{d x} [3]$

Step 1.4

Differentiate using the Constant Rule.

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Step 1.4.1

Since $3$ is constant with respect to $x$ , the derivative of $3$ with respect to $x$ is $0$ .

$4 x^{3} + 4 x + 8 + 0$

Step 1.4.2

Add $4 x^{3} + 4 x + 8$ and $0$ .

$4 x^{3} + 4 x + 8$

Step 2

Find the second derivative of the function.

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Step 2.1

By the Sum Rule, the derivative of $4 x^{3} + 4 x + 8$ with respect to $x$ is $\frac{d}{d x} [4 x^{3}] + \frac{d}{d x} [4 x] + \frac{d}{d x} [8]$ .

$f'' (x) = \frac{d}{d x} (4 x^{3}) + \frac{d}{d x} (4 x) + \frac{d}{d x} (8)$

Step 2.2

Evaluate $\frac{d}{d x} [4 x^{3}]$ .

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Step 2.2.1

Since $4$ is constant with respect to $x$ , the derivative of $4 x^{3}$ with respect to $x$ is $4 \frac{d}{d x} [x^{3}]$ .

$f'' (x) = 4 \frac{d}{d x} (x^{3}) + \frac{d}{d x} (4 x) + \frac{d}{d x} (8)$

Step 2.2.2

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

$f'' (x) = 4 (3 x^{2}) + \frac{d}{d x} (4 x) + \frac{d}{d x} (8)$

Step 2.2.3

Multiply $3$ by $4$ .

$f'' (x) = 12 x^{2} + \frac{d}{d x} (4 x) + \frac{d}{d x} (8)$

Step 2.3

Evaluate $\frac{d}{d x} [4 x]$ .

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Step 2.3.1

Since $4$ is constant with respect to $x$ , the derivative of $4 x$ with respect to $x$ is $4 \frac{d}{d x} [x]$ .

$f'' (x) = 12 x^{2} + 4 \frac{d}{d x} (x) + \frac{d}{d x} (8)$

Step 2.3.2

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

$f'' (x) = 12 x^{2} + 4 \cdot 1 + \frac{d}{d x} (8)$

Step 2.3.3

Multiply $4$ by $1$ .

$f'' (x) = 12 x^{2} + 4 + \frac{d}{d x} (8)$

Step 2.4

Differentiate using the Constant Rule.

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Step 2.4.1

Since $8$ is constant with respect to $x$ , the derivative of $8$ with respect to $x$ is $0$ .

$f'' (x) = 12 x^{2} + 4 + 0$

Step 2.4.2

Add $12 x^{2} + 4$ and $0$ .

$f'' (x) = 12 x^{2} + 4$

Step 3

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

$4 x^{3} + 4 x + 8 = 0$

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.

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Step 4.1.1.1

By the Sum Rule, the derivative of $x^{4} + 2 x^{2} + 8 x + 3$ with respect to $x$ is $\frac{d}{d x} [x^{4}] + \frac{d}{d x} [2 x^{2}] + \frac{d}{d x} [8 x] + \frac{d}{d x} [3]$ .

$\frac{d}{d x} [x^{4}] + \frac{d}{d x} [2 x^{2}] + \frac{d}{d x} [8 x] + \frac{d}{d x} [3]$

Step 4.1.1.2

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 4$ .

$4 x^{3} + \frac{d}{d x} [2 x^{2}] + \frac{d}{d x} [8 x] + \frac{d}{d x} [3]$

Step 4.1.2

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

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Step 4.1.2.1

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

$4 x^{3} + 2 \frac{d}{d x} [x^{2}] + \frac{d}{d x} [8 x] + \frac{d}{d x} [3]$

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 $n = 2$ .

$4 x^{3} + 2 (2 x) + \frac{d}{d x} [8 x] + \frac{d}{d x} [3]$

Step 4.1.2.3

Multiply $2$ by $2$ .

$4 x^{3} + 4 x + \frac{d}{d x} [8 x] + \frac{d}{d x} [3]$

Step 4.1.3

Evaluate $\frac{d}{d x} [8 x]$ .

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Step 4.1.3.1

Since $8$ is constant with respect to $x$ , the derivative of $8 x$ with respect to $x$ is $8 \frac{d}{d x} [x]$ .

$4 x^{3} + 4 x + 8 \frac{d}{d x} [x] + \frac{d}{d x} [3]$

Step 4.1.3.2

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

$4 x^{3} + 4 x + 8 \cdot 1 + \frac{d}{d x} [3]$

Step 4.1.3.3

Multiply $8$ by $1$ .

$4 x^{3} + 4 x + 8 + \frac{d}{d x} [3]$

Step 4.1.4

Differentiate using the Constant Rule.

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Step 4.1.4.1

Since $3$ is constant with respect to $x$ , the derivative of $3$ with respect to $x$ is $0$ .

$4 x^{3} + 4 x + 8 + 0$

Step 4.1.4.2

Add $4 x^{3} + 4 x + 8$ and $0$ .

$f' (x) = 4 x^{3} + 4 x + 8$

Step 4.2

The first derivative of $f (x)$ with respect to $x$ is $4 x^{3} + 4 x + 8$ .

$4 x^{3} + 4 x + 8$

Step 5

Set the first derivative equal to $0$ then solve the equation $4 x^{3} + 4 x + 8 = 0$ .

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Step 5.1

Set the first derivative equal to $0$ .

$4 x^{3} + 4 x + 8 = 0$

Step 5.2

Factor the left side of the equation.

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Step 5.2.1

Factor $4$ out of $4 x^{3} + 4 x + 8$ .

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Step 5.2.1.1

Factor $4$ out of $4 x^{3}$ .

$4 (x^{3}) + 4 x + 8 = 0$

Step 5.2.1.2

Factor $4$ out of $4 x$ .

$4 (x^{3}) + 4 (x) + 8 = 0$

Step 5.2.1.3

Factor $4$ out of $8$ .

$4 (x^{3}) + 4 x + 4 \cdot 2 = 0$

Step 5.2.1.4

Factor $4$ out of $4 (x^{3}) + 4 x$ .

$4 (x^{3} + x) + 4 \cdot 2 = 0$

Step 5.2.1.5

Factor $4$ out of $4 (x^{3} + x) + 4 \cdot 2$ .

$4 (x^{3} + x + 2) = 0$

Step 5.2.2

Factor.

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Step 5.2.2.1

Factor $x^{3} + x + 2$ using the rational roots test.

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Step 5.2.2.1.1

If a polynomial function has integer coefficients, then every rational zero will have the form $\frac{p}{q}$ where $p$ is a factor of the constant and $q$ is a factor of the leading coefficient.

$p = \pm 1, \pm 2$

$q = \pm 1$

Step 5.2.2.1.2

Find every combination of $\pm \frac{p}{q}$ . These are the possible roots of the polynomial function.

$\pm 1, \pm 2$

Step 5.2.2.1.3

Substitute $- 1$ and simplify the expression. In this case, the expression is equal to $0$ so $- 1$ is a root of the polynomial.

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Step 5.2.2.1.3.1

Substitute $- 1$ into the polynomial.

${(- 1)}^{3} - 1 + 2$

Step 5.2.2.1.3.2

Raise $- 1$ to the power of $3$ .

$- 1 - 1 + 2$

Step 5.2.2.1.3.3

Subtract $1$ from $- 1$ .

$- 2 + 2$

Step 5.2.2.1.3.4

Add $- 2$ and $2$ .

$0$

Step 5.2.2.1.4

Since $- 1$ is a known root, divide the polynomial by $x + 1$ to find the quotient polynomial. This polynomial can then be used to find the remaining roots.

$\frac{x^{3} + x + 2}{x + 1}$

Step 5.2.2.1.5

Divide $x^{3} + x + 2$ by $x + 1$ .

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Step 5.2.2.1.5.1

Set up the polynomials to be divided. If there is not a term for every exponent, insert one with a value of $0$ .

$x$

$1$

$x^{3}$

$0 x^{2}$

$x$

$2$

Step 5.2.2.1.5.2

Divide the highest order term in the dividend $x^{3}$ by the highest order term in divisor $x$ .

					$x^{2}$
	$x$	+	$1$		$x^{3}$	+	$0 x^{2}$	+	$x$	+	$2$

Step 5.2.2.1.5.3

Multiply the new quotient term by the divisor.

				$x^{2}$
$x$	+	$1$		$x^{3}$	+	$0 x^{2}$	+	$x$	+	$2$
			+	$x^{3}$	+	$x^{2}$

Step 5.2.2.1.5.4

The expression needs to be subtracted from the dividend, so change all the signs in $x^{3} + x^{2}$

				$x^{2}$
$x$	+	$1$		$x^{3}$	+	$0 x^{2}$	+	$x$	+	$2$
			-	$x^{3}$	-	$x^{2}$

Step 5.2.2.1.5.5

After changing the signs, add the last dividend from the multiplied polynomial to find the new dividend.

				$x^{2}$
$x$	+	$1$		$x^{3}$	+	$0 x^{2}$	+	$x$	+	$2$
			-	$x^{3}$	-	$x^{2}$
					-	$x^{2}$

Step 5.2.2.1.5.6

Pull the next terms from the original dividend down into the current dividend.

				$x^{2}$
$x$	+	$1$		$x^{3}$	+	$0 x^{2}$	+	$x$	+	$2$
			-	$x^{3}$	-	$x^{2}$
					-	$x^{2}$	+	$x$

Step 5.2.2.1.5.7

Divide the highest order term in the dividend $- x^{2}$ by the highest order term in divisor $x$ .

				$x^{2}$	-	$x$
$x$	+	$1$		$x^{3}$	+	$0 x^{2}$	+	$x$	+	$2$
			-	$x^{3}$	-	$x^{2}$
					-	$x^{2}$	+	$x$

Step 5.2.2.1.5.8

Multiply the new quotient term by the divisor.

				$x^{2}$	-	$x$
$x$	+	$1$		$x^{3}$	+	$0 x^{2}$	+	$x$	+	$2$
			-	$x^{3}$	-	$x^{2}$
					-	$x^{2}$	+	$x$
					-	$x^{2}$	-	$x$

Step 5.2.2.1.5.9

The expression needs to be subtracted from the dividend, so change all the signs in $- x^{2} - x$

				$x^{2}$	-	$x$
$x$	+	$1$		$x^{3}$	+	$0 x^{2}$	+	$x$	+	$2$
			-	$x^{3}$	-	$x^{2}$
					-	$x^{2}$	+	$x$
					+	$x^{2}$	+	$x$

Step 5.2.2.1.5.10

After changing the signs, add the last dividend from the multiplied polynomial to find the new dividend.

				$x^{2}$	-	$x$
$x$	+	$1$		$x^{3}$	+	$0 x^{2}$	+	$x$	+	$2$
			-	$x^{3}$	-	$x^{2}$
					-	$x^{2}$	+	$x$
					+	$x^{2}$	+	$x$
							+	$2 x$

Step 5.2.2.1.5.11

Pull the next terms from the original dividend down into the current dividend.

				$x^{2}$	-	$x$
$x$	+	$1$		$x^{3}$	+	$0 x^{2}$	+	$x$	+	$2$
			-	$x^{3}$	-	$x^{2}$
					-	$x^{2}$	+	$x$
					+	$x^{2}$	+	$x$
							+	$2 x$	+	$2$

Step 5.2.2.1.5.12

Divide the highest order term in the dividend $2 x$ by the highest order term in divisor $x$ .

				$x^{2}$	-	$x$	+	$2$
$x$	+	$1$		$x^{3}$	+	$0 x^{2}$	+	$x$	+	$2$
			-	$x^{3}$	-	$x^{2}$
					-	$x^{2}$	+	$x$
					+	$x^{2}$	+	$x$
							+	$2 x$	+	$2$

Step 5.2.2.1.5.13

Multiply the new quotient term by the divisor.

				$x^{2}$	-	$x$	+	$2$
$x$	+	$1$		$x^{3}$	+	$0 x^{2}$	+	$x$	+	$2$
			-	$x^{3}$	-	$x^{2}$
					-	$x^{2}$	+	$x$
					+	$x^{2}$	+	$x$
							+	$2 x$	+	$2$
							+	$2 x$	+	$2$

Step 5.2.2.1.5.14

The expression needs to be subtracted from the dividend, so change all the signs in $2 x + 2$

				$x^{2}$	-	$x$	+	$2$
$x$	+	$1$		$x^{3}$	+	$0 x^{2}$	+	$x$	+	$2$
			-	$x^{3}$	-	$x^{2}$
					-	$x^{2}$	+	$x$
					+	$x^{2}$	+	$x$
							+	$2 x$	+	$2$
							-	$2 x$	-	$2$

Step 5.2.2.1.5.15

After changing the signs, add the last dividend from the multiplied polynomial to find the new dividend.

				$x^{2}$	-	$x$	+	$2$
$x$	+	$1$		$x^{3}$	+	$0 x^{2}$	+	$x$	+	$2$
			-	$x^{3}$	-	$x^{2}$
					-	$x^{2}$	+	$x$
					+	$x^{2}$	+	$x$
							+	$2 x$	+	$2$
							-	$2 x$	-	$2$
										$0$

Step 5.2.2.1.5.16

Since the remander is $0$ , the final answer is the quotient.

$x^{2} - x + 2$

Step 5.2.2.1.6

Write $x^{3} + x + 2$ as a set of factors.

$4 ((x + 1) (x^{2} - x + 2)) = 0$

Step 5.2.2.2

Remove unnecessary parentheses.

$4 (x + 1) (x^{2} - x + 2) = 0$

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 $0$ .

$x + 1 = 0$

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

Step 5.4

Set $x + 1$ equal to $0$ and solve for $x$ .

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Step 5.4.1

Set $x + 1$ equal to $0$ .

$x + 1 = 0$

Step 5.4.2

Subtract $1$ from both sides of the equation.

$x = - 1$

Step 5.5

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

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Step 5.5.1

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

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

Step 5.5.2

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

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Step 5.5.2.1

Use the quadratic formula to find the solutions.

$\frac{- b \pm \sqrt{b^{2} - 4 (a c)}}{2 a}$

Step 5.5.2.2

Substitute the values $a = 1$ , $b = - 1$ , and $c = 2$ into the quadratic formula and solve for $x$ .

$\frac{1 \pm \sqrt{{(- 1)}^{2} - 4 \cdot (1 \cdot 2)}}{2 \cdot 1}$

Step 5.5.2.3

Simplify.

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Step 5.5.2.3.1

Simplify the numerator.

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Step 5.5.2.3.1.1

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

$x = \frac{1 \pm \sqrt{1 - 4 \cdot 1 \cdot 2}}{2 \cdot 1}$

Step 5.5.2.3.1.2

Multiply $- 4 \cdot 1 \cdot 2$ .

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Step 5.5.2.3.1.2.1

Multiply $- 4$ by $1$ .

$x = \frac{1 \pm \sqrt{1 - 4 \cdot 2}}{2 \cdot 1}$

Step 5.5.2.3.1.2.2

Multiply $- 4$ by $2$ .

$x = \frac{1 \pm \sqrt{1 - 8}}{2 \cdot 1}$

Step 5.5.2.3.1.3

Subtract $8$ from $1$ .

$x = \frac{1 \pm \sqrt{- 7}}{2 \cdot 1}$

Step 5.5.2.3.1.4

Rewrite $- 7$ as $- 1 (7)$ .

$x = \frac{1 \pm \sqrt{- 1 \cdot 7}}{2 \cdot 1}$

Step 5.5.2.3.1.5

Rewrite $\sqrt{- 1 (7)}$ as $\sqrt{- 1} \cdot \sqrt{7}$ .

$x = \frac{1 \pm \sqrt{- 1} \cdot \sqrt{7}}{2 \cdot 1}$

Step 5.5.2.3.1.6

Rewrite $\sqrt{- 1}$ as $i$ .

$x = \frac{1 \pm i \sqrt{7}}{2 \cdot 1}$

Step 5.5.2.3.2

Multiply $2$ by $1$ .

$x = \frac{1 \pm i \sqrt{7}}{2}$

Step 5.5.2.4

Simplify the expression to solve for the $+$ portion of the $\pm$ .

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Step 5.5.2.4.1

Simplify the numerator.

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Step 5.5.2.4.1.1

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

$x = \frac{1 \pm \sqrt{1 - 4 \cdot 1 \cdot 2}}{2 \cdot 1}$

Step 5.5.2.4.1.2

Multiply $- 4 \cdot 1 \cdot 2$ .

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Step 5.5.2.4.1.2.1

Multiply $- 4$ by $1$ .

$x = \frac{1 \pm \sqrt{1 - 4 \cdot 2}}{2 \cdot 1}$

Step 5.5.2.4.1.2.2

Multiply $- 4$ by $2$ .

$x = \frac{1 \pm \sqrt{1 - 8}}{2 \cdot 1}$

Step 5.5.2.4.1.3

Subtract $8$ from $1$ .

$x = \frac{1 \pm \sqrt{- 7}}{2 \cdot 1}$

Step 5.5.2.4.1.4

Rewrite $- 7$ as $- 1 (7)$ .

$x = \frac{1 \pm \sqrt{- 1 \cdot 7}}{2 \cdot 1}$

Step 5.5.2.4.1.5

Rewrite $\sqrt{- 1 (7)}$ as $\sqrt{- 1} \cdot \sqrt{7}$ .

$x = \frac{1 \pm \sqrt{- 1} \cdot \sqrt{7}}{2 \cdot 1}$

Step 5.5.2.4.1.6

Rewrite $\sqrt{- 1}$ as $i$ .

$x = \frac{1 \pm i \sqrt{7}}{2 \cdot 1}$

Step 5.5.2.4.2

Multiply $2$ by $1$ .

$x = \frac{1 \pm i \sqrt{7}}{2}$

Step 5.5.2.4.3

Change the $\pm$ to $+$ .

$x = \frac{1 + i \sqrt{7}}{2}$

Step 5.5.2.5

Simplify the expression to solve for the $-$ portion of the $\pm$ .

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Step 5.5.2.5.1

Simplify the numerator.

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Step 5.5.2.5.1.1

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

$x = \frac{1 \pm \sqrt{1 - 4 \cdot 1 \cdot 2}}{2 \cdot 1}$

Step 5.5.2.5.1.2

Multiply $- 4 \cdot 1 \cdot 2$ .

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Step 5.5.2.5.1.2.1

Multiply $- 4$ by $1$ .

$x = \frac{1 \pm \sqrt{1 - 4 \cdot 2}}{2 \cdot 1}$

Step 5.5.2.5.1.2.2

Multiply $- 4$ by $2$ .

$x = \frac{1 \pm \sqrt{1 - 8}}{2 \cdot 1}$

Step 5.5.2.5.1.3

Subtract $8$ from $1$ .

$x = \frac{1 \pm \sqrt{- 7}}{2 \cdot 1}$

Step 5.5.2.5.1.4

Rewrite $- 7$ as $- 1 (7)$ .

$x = \frac{1 \pm \sqrt{- 1 \cdot 7}}{2 \cdot 1}$

Step 5.5.2.5.1.5

Rewrite $\sqrt{- 1 (7)}$ as $\sqrt{- 1} \cdot \sqrt{7}$ .

$x = \frac{1 \pm \sqrt{- 1} \cdot \sqrt{7}}{2 \cdot 1}$

Step 5.5.2.5.1.6

Rewrite $\sqrt{- 1}$ as $i$ .

$x = \frac{1 \pm i \sqrt{7}}{2 \cdot 1}$

Step 5.5.2.5.2

Multiply $2$ by $1$ .

$x = \frac{1 \pm i \sqrt{7}}{2}$

Step 5.5.2.5.3

Change the $\pm$ to $-$ .

$x = \frac{1 - i \sqrt{7}}{2}$

Step 5.5.2.6

The final answer is the combination of both solutions.

$x = \frac{1 + i \sqrt{7}}{2}, \frac{1 - i \sqrt{7}}{2}$

Step 5.6

The final solution is all the values that make $4 (x + 1) (x^{2} - x + 2) = 0$ true.

$x = - 1, \frac{1 + i \sqrt{7}}{2}, \frac{1 - i \sqrt{7}}{2}$

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.

$x = - 1$

Step 8

Evaluate the second derivative at $x = - 1$ . If the second derivative is positive, then this is a local minimum. If it is negative, then this is a local maximum.

$12 {(- 1)}^{2} + 4$

Step 9

Evaluate the second derivative.

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Step 9.1

Simplify each term.

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Step 9.1.1

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

$12 \cdot 1 + 4$

Step 9.1.2

Multiply $12$ by $1$ .

$12 + 4$

Step 9.2

Add $12$ and $4$ .

$16$

Step 10

$x = - 1$ is a local minimum because the value of the second derivative is positive. This is referred to as the second derivative test.

$x = - 1$ is a local minimum

Step 11

Find the y-value when $x = - 1$ .

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Step 11.1

Replace the variable $x$ with $- 1$ in the expression.

$f (- 1) = {(- 1)}^{4} + 2 {(- 1)}^{2} + 8 (- 1) + 3$

Step 11.2

Simplify the result.

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Step 11.2.1

Simplify each term.

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Step 11.2.1.1

Raise $- 1$ to the power of $4$ .

$f (- 1) = 1 + 2 {(- 1)}^{2} + 8 (- 1) + 3$

Step 11.2.1.2

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

$f (- 1) = 1 + 2 \cdot 1 + 8 (- 1) + 3$

Step 11.2.1.3

Multiply $2$ by $1$ .

$f (- 1) = 1 + 2 + 8 (- 1) + 3$

Step 11.2.1.4

Multiply $8$ by $- 1$ .

$f (- 1) = 1 + 2 - 8 + 3$

Step 11.2.2

Simplify by adding and subtracting.

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Step 11.2.2.1

Add $1$ and $2$ .

$f (- 1) = 3 - 8 + 3$

Step 11.2.2.2

Subtract $8$ from $3$ .

$f (- 1) = - 5 + 3$

Step 11.2.2.3

Add $- 5$ and $3$ .

$f (- 1) = - 2$

Step 11.2.3

The final answer is $- 2$ .

$y = - 2$

Step 12

These are the local extrema for $f (x) = x^{4} + 2 x^{2} + 8 x + 3$ .

$(- 1, - 2)$ is a local minima

Step 13