Calculus Examples

$f (x) = \frac{1}{2} x^{2} + 6 x + 7$

Step 1

Find the first derivative.

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Step 1.1

Find the first derivative.

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Step 1.1.1

By the Sum Rule, the derivative of $\frac{1}{2} x^{2} + 6 x + 7$ with respect to $x$ is $\frac{d}{d x} [\frac{1}{2} x^{2}] + \frac{d}{d x} [6 x] + \frac{d}{d x} [7]$ .

$\frac{d}{d x} [\frac{1}{2} x^{2}] + \frac{d}{d x} [6 x] + \frac{d}{d x} [7]$

Step 1.1.2

Evaluate $\frac{d}{d x} [\frac{1}{2} x^{2}]$ .

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Step 1.1.2.1

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

$\frac{1}{2} \frac{d}{d x} [x^{2}] + \frac{d}{d x} [6 x] + \frac{d}{d x} [7]$

Step 1.1.2.2

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

$\frac{1}{2} (2 x) + \frac{d}{d x} [6 x] + \frac{d}{d x} [7]$

Step 1.1.2.3

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

$\frac{2}{2} x + \frac{d}{d x} [6 x] + \frac{d}{d x} [7]$

Step 1.1.2.4

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

$\frac{2 x}{2} + \frac{d}{d x} [6 x] + \frac{d}{d x} [7]$

Step 1.1.2.5

Cancel the common factor of $2$ .

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Step 1.1.2.5.1

Cancel the common factor.

$\frac{2 x}{2} + \frac{d}{d x} [6 x] + \frac{d}{d x} [7]$

Step 1.1.2.5.2

Divide $x$ by $1$ .

$x + \frac{d}{d x} [6 x] + \frac{d}{d x} [7]$

Step 1.1.3

Evaluate $\frac{d}{d x} [6 x]$ .

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Step 1.1.3.1

Since $6$ is constant with respect to $x$ , the derivative of $6 x$ with respect to $x$ is $6 \frac{d}{d x} [x]$ .

$x + 6 \frac{d}{d x} [x] + \frac{d}{d x} [7]$

Step 1.1.3.2

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

$x + 6 \cdot 1 + \frac{d}{d x} [7]$

Step 1.1.3.3

Multiply $6$ by $1$ .

$x + 6 + \frac{d}{d x} [7]$

Step 1.1.4

Differentiate using the Constant Rule.

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Step 1.1.4.1

Since $7$ is constant with respect to $x$ , the derivative of $7$ with respect to $x$ is $0$ .

$x + 6 + 0$

Step 1.1.4.2

Add $x + 6$ and $0$ .

$f' (x) = x + 6$

Step 1.2

The first derivative of $f (x)$ with respect to $x$ is $x + 6$ .

$x + 6$

Step 2

Set the first derivative equal to $0$ then solve the equation $x + 6 = 0$ .

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Step 2.1

Set the first derivative equal to $0$ .

$x + 6 = 0$

Step 2.2

Subtract $6$ from both sides of the equation.

$x = - 6$

Step 3

Find the values where the derivative is undefined.

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Step 3.1

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 4

Evaluate $\frac{1}{2} x^{2} + 6 x + 7$ at each $x$ value where the derivative is $0$ or undefined.

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Step 4.1

Evaluate at $x = - 6$ .

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Step 4.1.1

Substitute $- 6$ for $x$ .

$\frac{1}{2} \cdot {(- 6)}^{2} + 6 (- 6) + 7$

Step 4.1.2

Simplify.

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Step 4.1.2.1

Simplify each term.

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Step 4.1.2.1.1

Raise $- 6$ to the power of $2$ .

$\frac{1}{2} \cdot 36 + 6 (- 6) + 7$

Step 4.1.2.1.2

Cancel the common factor of $2$ .

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Step 4.1.2.1.2.1

Factor $2$ out of $36$ .

$\frac{1}{2} \cdot (2 (18)) + 6 (- 6) + 7$

Step 4.1.2.1.2.2

Cancel the common factor.

$\frac{1}{2} \cdot (2 \cdot 18) + 6 (- 6) + 7$

Step 4.1.2.1.2.3

Rewrite the expression.

$18 + 6 (- 6) + 7$

Step 4.1.2.1.3

Multiply $6$ by $- 6$ .

$18 - 36 + 7$

Step 4.1.2.2

Simplify by adding and subtracting.

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Step 4.1.2.2.1

Subtract $36$ from $18$ .

$- 18 + 7$

Step 4.1.2.2.2

Add $- 18$ and $7$ .

$- 11$

Step 4.2

List all of the points.

$(- 6, - 11)$

Step 5