Precalculus Examples

$f (x) = - x (x + 2) (x - 3)$

Step 1

Consider the difference quotient formula.

$\frac{f (x + h) - f (x)}{h}$

Step 2

Find the components of the definition.

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Step 2.1

Evaluate the function at $x = x + h$ .

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Step 2.1.1

Replace the variable $x$ with $x + h$ in the expression.

$f (x + h) = - (x + h) ((x + h) + 2) ((x + h) - 3)$

Step 2.1.2

Simplify the result.

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Step 2.1.2.1

Apply the distributive property.

$f (x + h) = (- x - h) ((x + h) + 2) ((x + h) - 3)$

Step 2.1.2.2

Expand $(- x - h) (x + h + 2)$ by multiplying each term in the first expression by each term in the second expression.

$f (x + h) = (- x \cdot x - x h - x \cdot 2 - h x - h \cdot h - h \cdot 2) ((x + h) - 3)$

Step 2.1.2.3

Simplify each term.

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Step 2.1.2.3.1

Multiply $x$ by $x$ by adding the exponents.

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Step 2.1.2.3.1.1

Move $x$ .

$f (x + h) = (- (x \cdot x) - x h - x \cdot 2 - h x - h \cdot h - h \cdot 2) ((x + h) - 3)$

Step 2.1.2.3.1.2

Multiply $x$ by $x$ .

$f (x + h) = (- x^{2} - x h - x \cdot 2 - h x - h \cdot h - h \cdot 2) ((x + h) - 3)$

Step 2.1.2.3.2

Multiply $2$ by $- 1$ .

$f (x + h) = (- x^{2} - x h - 2 x - h x - h \cdot h - h \cdot 2) ((x + h) - 3)$

Step 2.1.2.3.3

Multiply $h$ by $h$ by adding the exponents.

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Step 2.1.2.3.3.1

Move $h$ .

$f (x + h) = (- x^{2} - x h - 2 x - h x - (h \cdot h) - h \cdot 2) ((x + h) - 3)$

Step 2.1.2.3.3.2

Multiply $h$ by $h$ .

$f (x + h) = (- x^{2} - x h - 2 x - h x - h^{2} - h \cdot 2) ((x + h) - 3)$

Step 2.1.2.3.4

Multiply $2$ by $- 1$ .

$f (x + h) = (- x^{2} - x h - 2 x - h x - h^{2} - 2 h) ((x + h) - 3)$

Step 2.1.2.4

Subtract $h x$ from $- x h$ .

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Step 2.1.2.4.1

Move $x$ .

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

Step 2.1.2.4.2

Subtract $h x$ from $- 1 h x$ .

$f (x + h) = (- x^{2} - 2 h x - 2 x - h^{2} - 2 h) ((x + h) - 3)$

Step 2.1.2.5

Expand $(- x^{2} - 2 h x - 2 x - h^{2} - 2 h) (x + h - 3)$ by multiplying each term in the first expression by each term in the second expression.

$f (x + h) = - x^{2} x - x^{2} h - x^{2} \cdot - 3 - 2 h x \cdot x - 2 h x h - 2 h x \cdot - 3 - 2 x \cdot x - 2 x h - 2 x \cdot - 3 - h^{2} x - h^{2} h - h^{2} \cdot - 3 - 2 h x - 2 h \cdot h - 2 h \cdot - 3$

Step 2.1.2.6

Simplify each term.

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Step 2.1.2.6.1

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

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Step 2.1.2.6.1.1

Move $x$ .

$f (x + h) = - (x \cdot x^{2}) - x^{2} h - x^{2} \cdot - 3 - 2 h x \cdot x - 2 h x h - 2 h x \cdot - 3 - 2 x \cdot x - 2 x h - 2 x \cdot - 3 - h^{2} x - h^{2} h - h^{2} \cdot - 3 - 2 h x - 2 h \cdot h - 2 h \cdot - 3$

Step 2.1.2.6.1.2

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

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Step 2.1.2.6.1.2.1

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

Step 2.1.2.6.1.2.2

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

$f (x + h) = - x^{1 + 2} - x^{2} h - x^{2} \cdot - 3 - 2 h x \cdot x - 2 h x h - 2 h x \cdot - 3 - 2 x \cdot x - 2 x h - 2 x \cdot - 3 - h^{2} x - h^{2} h - h^{2} \cdot - 3 - 2 h x - 2 h \cdot h - 2 h \cdot - 3$

Step 2.1.2.6.1.3

Add $1$ and $2$ .

$f (x + h) = - x^{3} - x^{2} h - x^{2} \cdot - 3 - 2 h x \cdot x - 2 h x h - 2 h x \cdot - 3 - 2 x \cdot x - 2 x h - 2 x \cdot - 3 - h^{2} x - h^{2} h - h^{2} \cdot - 3 - 2 h x - 2 h \cdot h - 2 h \cdot - 3$

Step 2.1.2.6.2

Multiply $- 3$ by $- 1$ .

$f (x + h) = - x^{3} - x^{2} h + 3 x^{2} - 2 h x \cdot x - 2 h x h - 2 h x \cdot - 3 - 2 x \cdot x - 2 x h - 2 x \cdot - 3 - h^{2} x - h^{2} h - h^{2} \cdot - 3 - 2 h x - 2 h \cdot h - 2 h \cdot - 3$

Step 2.1.2.6.3

Multiply $x$ by $x$ by adding the exponents.

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Step 2.1.2.6.3.1

Move $x$ .

$f (x + h) = - x^{3} - x^{2} h + 3 x^{2} - 2 h (x \cdot x) - 2 h x h - 2 h x \cdot - 3 - 2 x \cdot x - 2 x h - 2 x \cdot - 3 - h^{2} x - h^{2} h - h^{2} \cdot - 3 - 2 h x - 2 h \cdot h - 2 h \cdot - 3$

Step 2.1.2.6.3.2

Multiply $x$ by $x$ .

$f (x + h) = - x^{3} - x^{2} h + 3 x^{2} - 2 h x^{2} - 2 h x h - 2 h x \cdot - 3 - 2 x \cdot x - 2 x h - 2 x \cdot - 3 - h^{2} x - h^{2} h - h^{2} \cdot - 3 - 2 h x - 2 h \cdot h - 2 h \cdot - 3$

Step 2.1.2.6.4

Multiply $h$ by $h$ by adding the exponents.

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Step 2.1.2.6.4.1

Move $h$ .

$f (x + h) = - x^{3} - x^{2} h + 3 x^{2} - 2 h x^{2} - 2 (h \cdot h) x - 2 h x \cdot - 3 - 2 x \cdot x - 2 x h - 2 x \cdot - 3 - h^{2} x - h^{2} h - h^{2} \cdot - 3 - 2 h x - 2 h \cdot h - 2 h \cdot - 3$

Step 2.1.2.6.4.2

Multiply $h$ by $h$ .

$f (x + h) = - x^{3} - x^{2} h + 3 x^{2} - 2 h x^{2} - 2 h^{2} x - 2 h x \cdot - 3 - 2 x \cdot x - 2 x h - 2 x \cdot - 3 - h^{2} x - h^{2} h - h^{2} \cdot - 3 - 2 h x - 2 h \cdot h - 2 h \cdot - 3$

Step 2.1.2.6.5

Multiply $- 3$ by $- 2$ .

$f (x + h) = - x^{3} - x^{2} h + 3 x^{2} - 2 h x^{2} - 2 h^{2} x + 6 h x - 2 x \cdot x - 2 x h - 2 x \cdot - 3 - h^{2} x - h^{2} h - h^{2} \cdot - 3 - 2 h x - 2 h \cdot h - 2 h \cdot - 3$

Step 2.1.2.6.6

Multiply $x$ by $x$ by adding the exponents.

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Step 2.1.2.6.6.1

Move $x$ .

$f (x + h) = - x^{3} - x^{2} h + 3 x^{2} - 2 h x^{2} - 2 h^{2} x + 6 h x - 2 (x \cdot x) - 2 x h - 2 x \cdot - 3 - h^{2} x - h^{2} h - h^{2} \cdot - 3 - 2 h x - 2 h \cdot h - 2 h \cdot - 3$

Step 2.1.2.6.6.2

Multiply $x$ by $x$ .

$f (x + h) = - x^{3} - x^{2} h + 3 x^{2} - 2 h x^{2} - 2 h^{2} x + 6 h x - 2 x^{2} - 2 x h - 2 x \cdot - 3 - h^{2} x - h^{2} h - h^{2} \cdot - 3 - 2 h x - 2 h \cdot h - 2 h \cdot - 3$

Step 2.1.2.6.7

Multiply $- 3$ by $- 2$ .

$f (x + h) = - x^{3} - x^{2} h + 3 x^{2} - 2 h x^{2} - 2 h^{2} x + 6 h x - 2 x^{2} - 2 x h + 6 x - h^{2} x - h^{2} h - h^{2} \cdot - 3 - 2 h x - 2 h \cdot h - 2 h \cdot - 3$

Step 2.1.2.6.8

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

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Step 2.1.2.6.8.1

Move $h$ .

$f (x + h) = - x^{3} - x^{2} h + 3 x^{2} - 2 h x^{2} - 2 h^{2} x + 6 h x - 2 x^{2} - 2 x h + 6 x - h^{2} x - (h \cdot h^{2}) - h^{2} \cdot - 3 - 2 h x - 2 h \cdot h - 2 h \cdot - 3$

Step 2.1.2.6.8.2

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

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Step 2.1.2.6.8.2.1

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

$f (x + h) = - x^{3} - x^{2} h + 3 x^{2} - 2 h x^{2} - 2 h^{2} x + 6 h x - 2 x^{2} - 2 x h + 6 x - h^{2} x - (h \cdot h^{2}) - h^{2} \cdot - 3 - 2 h x - 2 h \cdot h - 2 h \cdot - 3$

Step 2.1.2.6.8.2.2

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

$f (x + h) = - x^{3} - x^{2} h + 3 x^{2} - 2 h x^{2} - 2 h^{2} x + 6 h x - 2 x^{2} - 2 x h + 6 x - h^{2} x - h^{1 + 2} - h^{2} \cdot - 3 - 2 h x - 2 h \cdot h - 2 h \cdot - 3$

Step 2.1.2.6.8.3

Add $1$ and $2$ .

$f (x + h) = - x^{3} - x^{2} h + 3 x^{2} - 2 h x^{2} - 2 h^{2} x + 6 h x - 2 x^{2} - 2 x h + 6 x - h^{2} x - h^{3} - h^{2} \cdot - 3 - 2 h x - 2 h \cdot h - 2 h \cdot - 3$

Step 2.1.2.6.9

Multiply $- 3$ by $- 1$ .

$f (x + h) = - x^{3} - x^{2} h + 3 x^{2} - 2 h x^{2} - 2 h^{2} x + 6 h x - 2 x^{2} - 2 x h + 6 x - h^{2} x - h^{3} + 3 h^{2} - 2 h x - 2 h \cdot h - 2 h \cdot - 3$

Step 2.1.2.6.10

Multiply $h$ by $h$ by adding the exponents.

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Step 2.1.2.6.10.1

Move $h$ .

$f (x + h) = - x^{3} - x^{2} h + 3 x^{2} - 2 h x^{2} - 2 h^{2} x + 6 h x - 2 x^{2} - 2 x h + 6 x - h^{2} x - h^{3} + 3 h^{2} - 2 h x - 2 (h \cdot h) - 2 h \cdot - 3$

Step 2.1.2.6.10.2

Multiply $h$ by $h$ .

$f (x + h) = - x^{3} - x^{2} h + 3 x^{2} - 2 h x^{2} - 2 h^{2} x + 6 h x - 2 x^{2} - 2 x h + 6 x - h^{2} x - h^{3} + 3 h^{2} - 2 h x - 2 h^{2} - 2 h \cdot - 3$

Step 2.1.2.6.11

Multiply $- 3$ by $- 2$ .

$f (x + h) = - x^{3} - x^{2} h + 3 x^{2} - 2 h x^{2} - 2 h^{2} x + 6 h x - 2 x^{2} - 2 x h + 6 x - h^{2} x - h^{3} + 3 h^{2} - 2 h x - 2 h^{2} + 6 h$

Step 2.1.2.7

Subtract $2 h x^{2}$ from $- x^{2} h$ .

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Step 2.1.2.7.1

Move $x^{2}$ .

$f (x + h) = - x^{3} + 3 x^{2} - 1 h x^{2} - 2 h x^{2} - 2 h^{2} x + 6 h x - 2 x^{2} - 2 x h + 6 x - h^{2} x - h^{3} + 3 h^{2} - 2 h x - 2 h^{2} + 6 h$

Step 2.1.2.7.2

Subtract $2 h x^{2}$ from $- 1 h x^{2}$ .

$f (x + h) = - x^{3} + 3 x^{2} - 3 h x^{2} - 2 h^{2} x + 6 h x - 2 x^{2} - 2 x h + 6 x - h^{2} x - h^{3} + 3 h^{2} - 2 h x - 2 h^{2} + 6 h$

Step 2.1.2.8

Subtract $2 x^{2}$ from $3 x^{2}$ .

$f (x + h) = - x^{3} + x^{2} - 3 h x^{2} - 2 h^{2} x + 6 h x - 2 x h + 6 x - h^{2} x - h^{3} + 3 h^{2} - 2 h x - 2 h^{2} + 6 h$

Step 2.1.2.9

Subtract $h^{2} x$ from $- 2 h^{2} x$ .

$f (x + h) = - x^{3} + x^{2} - 3 h x^{2} - 3 h^{2} x + 6 h x - 2 x h + 6 x - h^{3} + 3 h^{2} - 2 h x - 2 h^{2} + 6 h$

Step 2.1.2.10

Subtract $2 x h$ from $6 h x$ .

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Step 2.1.2.10.1

Move $x$ .

$f (x + h) = - x^{3} + x^{2} - 3 h x^{2} - 3 h^{2} x + 6 h x - 2 h x + 6 x - h^{3} + 3 h^{2} - 2 h x - 2 h^{2} + 6 h$

Step 2.1.2.10.2

Subtract $2 h x$ from $6 h x$ .

$f (x + h) = - x^{3} + x^{2} - 3 h x^{2} - 3 h^{2} x + 4 h x + 6 x - h^{3} + 3 h^{2} - 2 h x - 2 h^{2} + 6 h$

Step 2.1.2.11

Subtract $2 h x$ from $4 h x$ .

$f (x + h) = - x^{3} + x^{2} - 3 h x^{2} - 3 h^{2} x + 6 x - h^{3} + 3 h^{2} + 2 h x - 2 h^{2} + 6 h$

Step 2.1.2.12

Subtract $2 h^{2}$ from $3 h^{2}$ .

$f (x + h) = - x^{3} + x^{2} - 3 h x^{2} - 3 h^{2} x + 6 x - h^{3} + h^{2} + 2 h x + 6 h$

Step 2.1.2.13

The final answer is $- x^{3} + x^{2} - 3 h x^{2} - 3 h^{2} x + 6 x - h^{3} + h^{2} + 2 h x + 6 h$ .

$- x^{3} + x^{2} - 3 h x^{2} - 3 h^{2} x + 6 x - h^{3} + h^{2} + 2 h x + 6 h$

Step 2.2

Reorder.

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Step 2.2.1

Move $6 x$ .

$- x^{3} + x^{2} - 3 h x^{2} - 3 h^{2} x - h^{3} + h^{2} + 2 h x + 6 h + 6 x$

Step 2.2.2

Move $x^{2}$ .

$- x^{3} - 3 h x^{2} - 3 h^{2} x - h^{3} + h^{2} + 2 h x + x^{2} + 6 h + 6 x$

Step 2.2.3

Move $- x^{3}$ .

$- 3 h x^{2} - 3 h^{2} x - h^{3} - x^{3} + h^{2} + 2 h x + x^{2} + 6 h + 6 x$

Step 2.2.4

Move $- 3 h x^{2}$ .

$- 3 h^{2} x - h^{3} - 3 h x^{2} - x^{3} + h^{2} + 2 h x + x^{2} + 6 h + 6 x$

Step 2.2.5

Reorder $- 3 h^{2} x$ and $- h^{3}$ .

$- h^{3} - 3 h^{2} x - 3 h x^{2} - x^{3} + h^{2} + 2 h x + x^{2} + 6 h + 6 x$

Step 2.3

Find the components of the definition.

$f (x + h) = - h^{3} - 3 h^{2} x - 3 h x^{2} - x^{3} + h^{2} + 2 h x + x^{2} + 6 h + 6 x$

$f (x) = - x^{3} + x^{2} + 6 x$

$f (x + h) = - h^{3} - 3 h^{2} x - 3 h x^{2} - x^{3} + h^{2} + 2 h x + x^{2} + 6 h + 6 x$

$f (x) = - x^{3} + x^{2} + 6 x$

Step 3

Plug in the components.

$\frac{f (x + h) - f (x)}{h} = \frac{- h^{3} - 3 h^{2} x - 3 h x^{2} - x^{3} + h^{2} + 2 h x + x^{2} + 6 h + 6 x - (- x^{3} + x^{2} + 6 x)}{h}$

Step 4

Simplify.

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Step 4.1

Simplify the numerator.

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Step 4.1.1

Apply the distributive property.

$\frac{- h^{3} - 3 h^{2} x - 3 h x^{2} - x^{3} + h^{2} + 2 h x + x^{2} + 6 h + 6 x - - x^{3} - x^{2} - (6 x)}{h}$

Step 4.1.2

Simplify.

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Step 4.1.2.1

Multiply $- - x^{3}$ .

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Step 4.1.2.1.1

Multiply $- 1$ by $- 1$ .

$\frac{- h^{3} - 3 h^{2} x - 3 h x^{2} - x^{3} + h^{2} + 2 h x + x^{2} + 6 h + 6 x + 1 x^{3} - x^{2} - (6 x)}{h}$

Step 4.1.2.1.2

Multiply $x^{3}$ by $1$ .

$\frac{- h^{3} - 3 h^{2} x - 3 h x^{2} - x^{3} + h^{2} + 2 h x + x^{2} + 6 h + 6 x + x^{3} - x^{2} - (6 x)}{h}$

Step 4.1.2.2

Multiply $6$ by $- 1$ .

$\frac{- h^{3} - 3 h^{2} x - 3 h x^{2} - x^{3} + h^{2} + 2 h x + x^{2} + 6 h + 6 x + x^{3} - x^{2} - 6 x}{h}$

Step 4.1.3

Add $- x^{3}$ and $x^{3}$ .

$\frac{- h^{3} - 3 h^{2} x - 3 h x^{2} + h^{2} + 2 h x + x^{2} + 6 h + 6 x + 0 - x^{2} - 6 x}{h}$

Step 4.1.4

Add $- h^{3}$ and $0$ .

$\frac{- h^{3} - 3 h^{2} x - 3 h x^{2} + h^{2} + 2 h x + x^{2} + 6 h + 6 x - x^{2} - 6 x}{h}$

Step 4.1.5

Subtract $x^{2}$ from $x^{2}$ .

$\frac{- h^{3} - 3 h^{2} x - 3 h x^{2} + h^{2} + 2 h x + 6 h + 6 x + 0 - 6 x}{h}$

Step 4.1.6

Add $- h^{3}$ and $0$ .

$\frac{- h^{3} - 3 h^{2} x - 3 h x^{2} + h^{2} + 2 h x + 6 h + 6 x - 6 x}{h}$

Step 4.1.7

Subtract $6 x$ from $6 x$ .

$\frac{- h^{3} - 3 h^{2} x - 3 h x^{2} + h^{2} + 2 h x + 6 h + 0}{h}$

Step 4.1.8

Add $- h^{3} - 3 h^{2} x - 3 h x^{2} + h^{2} + 2 h x + 6 h$ and $0$ .

$\frac{- h^{3} - 3 h^{2} x - 3 h x^{2} + h^{2} + 2 h x + 6 h}{h}$

Step 4.1.9

Factor $h$ out of $- h^{3} - 3 h^{2} x - 3 h x^{2} + h^{2} + 2 h x + 6 h$ .

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Step 4.1.9.1

Factor $h$ out of $- h^{3}$ .

$\frac{h (- h^{2}) - 3 h^{2} x - 3 h x^{2} + h^{2} + 2 h x + 6 h}{h}$

Step 4.1.9.2

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

$\frac{h (- h^{2}) + h (- 3 h x) - 3 h x^{2} + h^{2} + 2 h x + 6 h}{h}$

Step 4.1.9.3

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

$\frac{h (- h^{2}) + h (- 3 h x) + h (- 3 x^{2}) + h^{2} + 2 h x + 6 h}{h}$

Step 4.1.9.4

Factor $h$ out of $h^{2}$ .

$\frac{h (- h^{2}) + h (- 3 h x) + h (- 3 x^{2}) + h (h) + 2 h x + 6 h}{h}$

Step 4.1.9.5

Factor $h$ out of $2 h x$ .

$\frac{h (- h^{2}) + h (- 3 h x) + h (- 3 x^{2}) + h (h) + h (2 x) + 6 h}{h}$

Step 4.1.9.6

Factor $h$ out of $6 h$ .

$\frac{h (- h^{2}) + h (- 3 h x) + h (- 3 x^{2}) + h (h) + h (2 x) + h \cdot 6}{h}$

Step 4.1.9.7

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

$\frac{h (- h^{2} - 3 h x) + h (- 3 x^{2}) + h (h) + h (2 x) + h \cdot 6}{h}$

Step 4.1.9.8

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

$\frac{h (- h^{2} - 3 h x - 3 x^{2}) + h (h) + h (2 x) + h \cdot 6}{h}$

Step 4.1.9.9

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

$\frac{h (- h^{2} - 3 h x - 3 x^{2} + h) + h (2 x) + h \cdot 6}{h}$

Step 4.1.9.10

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

$\frac{h (- h^{2} - 3 h x - 3 x^{2} + h + 2 x) + h \cdot 6}{h}$

Step 4.1.9.11

Factor $h$ out of $h (- h^{2} - 3 h x - 3 x^{2} + h + 2 x) + h \cdot 6$ .

$\frac{h (- h^{2} - 3 h x - 3 x^{2} + h + 2 x + 6)}{h}$

Step 4.2

Reduce the expression by cancelling the common factors.

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Step 4.2.1

Cancel the common factor of $h$ .

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Step 4.2.1.1

Cancel the common factor.

$\frac{h (- h^{2} - 3 h x - 3 x^{2} + h + 2 x + 6)}{h}$

Step 4.2.1.2

Divide $- h^{2} - 3 h x - 3 x^{2} + h + 2 x + 6$ by $1$ .

$- h^{2} - 3 h x - 3 x^{2} + h + 2 x + 6$

Step 4.2.2

Simplify the expression.

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Step 4.2.2.1

Move $h$ .

$- h^{2} - 3 x h - 3 x^{2} + h + 2 x + 6$

Step 4.2.2.2

Move $h$ .

$- h^{2} - 3 x h - 3 x^{2} + 2 x + h + 6$

Step 4.2.2.3

Move $- h^{2}$ .

$- 3 x h - 3 x^{2} - h^{2} + 2 x + h + 6$

Step 4.2.2.4

Reorder $- 3 x h$ and $- 3 x^{2}$ .

$- 3 x^{2} - 3 x h - h^{2} + 2 x + h + 6$

Step 5