Calculus Examples

$f (x) = x^{8} - 8 x^{7}$

Step 1

Find the first derivative.

Tap for more steps...

Step 1.1

Find the first derivative.

Tap for more steps...

Step 1.1.1

Differentiate.

Tap for more steps...

Step 1.1.1.1

By the Sum Rule, the derivative of $x^{8} - 8 x^{7}$ with respect to $x$ is $\frac{d}{d x} [x^{8}] + \frac{d}{d x} [- 8 x^{7}]$ .

$\frac{d}{d x} [x^{8}] + \frac{d}{d x} [- 8 x^{7}]$

Step 1.1.1.2

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 8$ .

$8 x^{7} + \frac{d}{d x} [- 8 x^{7}]$

Step 1.1.2

Evaluate $\frac{d}{d x} [- 8 x^{7}]$ .

Tap for more steps...

Step 1.1.2.1

Since $- 8$ is constant with respect to $x$ , the derivative of $- 8 x^{7}$ with respect to $x$ is $- 8 \frac{d}{d x} [x^{7}]$ .

$8 x^{7} - 8 \frac{d}{d x} [x^{7}]$

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 $n = 7$ .

$8 x^{7} - 8 (7 x^{6})$

Step 1.1.2.3

Multiply $7$ by $- 8$ .

$f' (x) = 8 x^{7} - 56 x^{6}$

Step 1.2

The first derivative of $f (x)$ with respect to $x$ is $8 x^{7} - 56 x^{6}$ .

$8 x^{7} - 56 x^{6}$

Step 2

Set the first derivative equal to $0$ then solve the equation $8 x^{7} - 56 x^{6} = 0$ .

Tap for more steps...

Step 2.1

Set the first derivative equal to $0$ .

$8 x^{7} - 56 x^{6} = 0$

Step 2.2

Factor $8 x^{6}$ out of $8 x^{7} - 56 x^{6}$ .

Tap for more steps...

Step 2.2.1

Factor $8 x^{6}$ out of $8 x^{7}$ .

$8 x^{6} (x) - 56 x^{6} = 0$

Step 2.2.2

Factor $8 x^{6}$ out of $- 56 x^{6}$ .

$8 x^{6} (x) + 8 x^{6} (- 7) = 0$

Step 2.2.3

Factor $8 x^{6}$ out of $8 x^{6} (x) + 8 x^{6} (- 7)$ .

$8 x^{6} (x - 7) = 0$

Step 2.3

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

$x^{6} = 0$

$x - 7 = 0$

Step 2.4

Set $x^{6}$ equal to $0$ and solve for $x$ .

Tap for more steps...

Step 2.4.1

Set $x^{6}$ equal to $0$ .

$x^{6} = 0$

Step 2.4.2

Solve $x^{6} = 0$ for $x$ .

Tap for more steps...

Step 2.4.2.1

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

$x = \pm \sqrt[6]{0}$

Step 2.4.2.2

Simplify $\pm \sqrt[6]{0}$ .

Tap for more steps...

Step 2.4.2.2.1

Rewrite $0$ as $0^{6}$ .

$x = \pm \sqrt[6]{0^{6}}$

Step 2.4.2.2.2

Pull terms out from under the radical, assuming positive real numbers.

$x = \pm 0$

Step 2.4.2.2.3

Plus or minus $0$ is $0$ .

$x = 0$

Step 2.5

Set $x - 7$ equal to $0$ and solve for $x$ .

Tap for more steps...

Step 2.5.1

Set $x - 7$ equal to $0$ .

$x - 7 = 0$

Step 2.5.2

Add $7$ to both sides of the equation.

$x = 7$

Step 2.6

The final solution is all the values that make $8 x^{6} (x - 7) = 0$ true.

$x = 0, 7$

Step 3

Find the values where the derivative is undefined.

Tap for more steps...

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 $x^{8} - 8 x^{7}$ at each $x$ value where the derivative is $0$ or undefined.

Tap for more steps...

Step 4.1

Evaluate at $x = 0$ .

Tap for more steps...

Step 4.1.1

Substitute $0$ for $x$ .

${(0)}^{8} - 8 {(0)}^{7}$

Step 4.1.2

Simplify.

Tap for more steps...

Step 4.1.2.1

Simplify each term.

Tap for more steps...

Step 4.1.2.1.1

Raising $0$ to any positive power yields $0$ .

$0 - 8 {(0)}^{7}$

Step 4.1.2.1.2

Raising $0$ to any positive power yields $0$ .

$0 - 8 \cdot 0$

Step 4.1.2.1.3

Multiply $- 8$ by $0$ .

$0 + 0$

Step 4.1.2.2

Add $0$ and $0$ .

$0$

Step 4.2

Evaluate at $x = 7$ .

Tap for more steps...

Step 4.2.1

Substitute $7$ for $x$ .

${(7)}^{8} - 8 {(7)}^{7}$

Step 4.2.2

Simplify.

Tap for more steps...

Step 4.2.2.1

Simplify each term.

Tap for more steps...

Step 4.2.2.1.1

Raise $7$ to the power of $8$ .

$5764801 - 8 {(7)}^{7}$

Step 4.2.2.1.2

Raise $7$ to the power of $7$ .

$5764801 - 8 \cdot 823543$

Step 4.2.2.1.3

Multiply $- 8$ by $823543$ .

$5764801 - 6588344$

Step 4.2.2.2

Subtract $6588344$ from $5764801$ .

$- 823543$

Step 4.3

List all of the points.

$(0, 0), (7, - 823543)$

Step 5