Calculus Examples

$y = x^{3} - 15 x^{2} + 75 x - 2$

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

Differentiate.

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Step 1.1.1.1

By the Sum Rule, the derivative of $x^{3} - 15 x^{2} + 75 x - 2$ with respect to $x$ is $\frac{d}{d x} [x^{3}] + \frac{d}{d x} [- 15 x^{2}] + \frac{d}{d x} [75 x] + \frac{d}{d x} [- 2]$ .

$\frac{d}{d x} [x^{3}] + \frac{d}{d x} [- 15 x^{2}] + \frac{d}{d x} [75 x] + \frac{d}{d x} [- 2]$

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 $n = 3$ .

$3 x^{2} + \frac{d}{d x} [- 15 x^{2}] + \frac{d}{d x} [75 x] + \frac{d}{d x} [- 2]$

Step 1.1.2

Evaluate $\frac{d}{d x} [- 15 x^{2}]$ .

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Step 1.1.2.1

Since $- 15$ is constant with respect to $x$ , the derivative of $- 15 x^{2}$ with respect to $x$ is $- 15 \frac{d}{d x} [x^{2}]$ .

$3 x^{2} - 15 \frac{d}{d x} [x^{2}] + \frac{d}{d x} [75 x] + \frac{d}{d x} [- 2]$

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 $n = 2$ .

$3 x^{2} - 15 (2 x) + \frac{d}{d x} [75 x] + \frac{d}{d x} [- 2]$

Step 1.1.2.3

Multiply $2$ by $- 15$ .

$3 x^{2} - 30 x + \frac{d}{d x} [75 x] + \frac{d}{d x} [- 2]$

Step 1.1.3

Evaluate $\frac{d}{d x} [75 x]$ .

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Step 1.1.3.1

Since $75$ is constant with respect to $x$ , the derivative of $75 x$ with respect to $x$ is $75 \frac{d}{d x} [x]$ .

$3 x^{2} - 30 x + 75 \frac{d}{d x} [x] + \frac{d}{d x} [- 2]$

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 $n = 1$ .

$3 x^{2} - 30 x + 75 \cdot 1 + \frac{d}{d x} [- 2]$

Step 1.1.3.3

Multiply $75$ by $1$ .

$3 x^{2} - 30 x + 75 + \frac{d}{d x} [- 2]$

Step 1.1.4

Differentiate using the Constant Rule.

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Step 1.1.4.1

Since $- 2$ is constant with respect to $x$ , the derivative of $- 2$ with respect to $x$ is $0$ .

$3 x^{2} - 30 x + 75 + 0$

Step 1.1.4.2

Add $3 x^{2} - 30 x + 75$ and $0$ .

$f' (x) = 3 x^{2} - 30 x + 75$

Step 1.2

The first derivative of $f (x)$ with respect to $x$ is $3 x^{2} - 30 x + 75$ .

$3 x^{2} - 30 x + 75$

Step 2

Set the first derivative equal to $0$ then solve the equation $3 x^{2} - 30 x + 75 = 0$ .

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Step 2.1

Set the first derivative equal to $0$ .

$3 x^{2} - 30 x + 75 = 0$

Step 2.2

Factor the left side of the equation.

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Step 2.2.1

Factor $3$ out of $3 x^{2} - 30 x + 75$ .

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Step 2.2.1.1

Factor $3$ out of $3 x^{2}$ .

$3 (x^{2}) - 30 x + 75 = 0$

Step 2.2.1.2

Factor $3$ out of $- 30 x$ .

$3 (x^{2}) + 3 (- 10 x) + 75 = 0$

Step 2.2.1.3

Factor $3$ out of $75$ .

$3 x^{2} + 3 (- 10 x) + 3 \cdot 25 = 0$

Step 2.2.1.4

Factor $3$ out of $3 x^{2} + 3 (- 10 x)$ .

$3 (x^{2} - 10 x) + 3 \cdot 25 = 0$

Step 2.2.1.5

Factor $3$ out of $3 (x^{2} - 10 x) + 3 \cdot 25$ .

$3 (x^{2} - 10 x + 25) = 0$

Step 2.2.2

Factor using the perfect square rule.

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Step 2.2.2.1

Rewrite $25$ as $5^{2}$ .

$3 (x^{2} - 10 x + 5^{2}) = 0$

Step 2.2.2.2

Check that the middle term is two times the product of the numbers being squared in the first term and third term.

$10 x = 2 \cdot x \cdot 5$

Step 2.2.2.3

Rewrite the polynomial.

$3 (x^{2} - 2 \cdot x \cdot 5 + 5^{2}) = 0$

Step 2.2.2.4

Factor using the perfect square trinomial rule $a^{2} - 2 a b + b^{2} = {(a - b)}^{2}$ , where $a = x$ and $b = 5$ .

$3 {(x - 5)}^{2} = 0$

Step 2.3

Divide each term in $3 {(x - 5)}^{2} = 0$ by $3$ and simplify.

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Step 2.3.1

Divide each term in $3 {(x - 5)}^{2} = 0$ by $3$ .

$\frac{3 {(x - 5)}^{2}}{3} = \frac{0}{3}$

Step 2.3.2

Simplify the left side.

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Step 2.3.2.1

Cancel the common factor of $3$ .

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Step 2.3.2.1.1

Cancel the common factor.

$\frac{3 {(x - 5)}^{2}}{3} = \frac{0}{3}$

Step 2.3.2.1.2

Divide ${(x - 5)}^{2}$ by $1$ .

${(x - 5)}^{2} = \frac{0}{3}$

Step 2.3.3

Simplify the right side.

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Step 2.3.3.1

Divide $0$ by $3$ .

${(x - 5)}^{2} = 0$

Step 2.4

Set the $x - 5$ equal to $0$ .

$x - 5 = 0$

Step 2.5

Add $5$ to both sides of the equation.

$x = 5$

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 $x^{3} - 15 x^{2} + 75 x - 2$ at each $x$ value where the derivative is $0$ or undefined.

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Step 4.1

Evaluate at $x = 5$ .

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Step 4.1.1

Substitute $5$ for $x$ .

${(5)}^{3} - 15 {(5)}^{2} + 75 (5) - 2$

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 $5$ to the power of $3$ .

$125 - 15 {(5)}^{2} + 75 (5) - 2$

Step 4.1.2.1.2

Raise $5$ to the power of $2$ .

$125 - 15 \cdot 25 + 75 (5) - 2$

Step 4.1.2.1.3

Multiply $- 15$ by $25$ .

$125 - 375 + 75 (5) - 2$

Step 4.1.2.1.4

Multiply $75$ by $5$ .

$125 - 375 + 375 - 2$

Step 4.1.2.2

Simplify by adding and subtracting.

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Step 4.1.2.2.1

Subtract $375$ from $125$ .

$- 250 + 375 - 2$

Step 4.1.2.2.2

Add $- 250$ and $375$ .

$125 - 2$

Step 4.1.2.2.3

Subtract $2$ from $125$ .

$123$

Step 4.2

List all of the points.

$(5, 123)$

Step 5