Precalculus Examples

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

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.

$f (x + h) = 3 {(x + h)}^{2} - 2 (x + h) + 5$

Step 2.1.2

Simplify the result.

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Step 2.1.2.1

Simplify each term.

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Step 2.1.2.1.1

Rewrite ${(x + h)}^{2}$ as $(x + h) (x + h)$ .

$f (x + h) = 3 ((x + h) (x + h)) - 2 (x + h) + 5$

Step 2.1.2.1.2

Expand $(x + h) (x + h)$ using the FOIL Method.

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Step 2.1.2.1.2.1

Apply the distributive property.

$f (x + h) = 3 (x (x + h) + h (x + h)) - 2 (x + h) + 5$

Step 2.1.2.1.2.2

Apply the distributive property.

$f (x + h) = 3 (x \cdot x + x h + h (x + h)) - 2 (x + h) + 5$

Step 2.1.2.1.2.3

Apply the distributive property.

$f (x + h) = 3 (x \cdot x + x h + h x + h \cdot h) - 2 (x + h) + 5$

Step 2.1.2.1.3

Simplify and combine like terms.

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Step 2.1.2.1.3.1

Simplify each term.

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Step 2.1.2.1.3.1.1

Multiply $x$ by $x$ .

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

Step 2.1.2.1.3.1.2

Multiply $h$ by $h$ .

$f (x + h) = 3 (x^{2} + x h + h x + h^{2}) - 2 (x + h) + 5$

Step 2.1.2.1.3.2

Add $x h$ and $h x$ .

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Step 2.1.2.1.3.2.1

Reorder $x$ and $h$ .

$f (x + h) = 3 (x^{2} + h x + h x + h^{2}) - 2 (x + h) + 5$

Step 2.1.2.1.3.2.2

Add $h x$ and $h x$ .

$f (x + h) = 3 (x^{2} + 2 h x + h^{2}) - 2 (x + h) + 5$

Step 2.1.2.1.4

Apply the distributive property.

$f (x + h) = 3 x^{2} + 3 (2 h x) + 3 h^{2} - 2 (x + h) + 5$

Step 2.1.2.1.5

Multiply $2$ by $3$ .

$f (x + h) = 3 x^{2} + 6 (h x) + 3 h^{2} - 2 (x + h) + 5$

Step 2.1.2.1.6

Apply the distributive property.

$f (x + h) = 3 x^{2} + 6 h x + 3 h^{2} - 2 x - 2 h + 5$

Step 2.1.2.2

The final answer is $3 x^{2} + 6 h x + 3 h^{2} - 2 x - 2 h + 5$ .

$3 x^{2} + 6 h x + 3 h^{2} - 2 x - 2 h + 5$

Step 2.2

Reorder.

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Step 2.2.1

Move $- 2 x$ .

$3 x^{2} + 6 h x + 3 h^{2} - 2 h - 2 x + 5$

Step 2.2.2

Move $3 x^{2}$ .

$6 h x + 3 h^{2} + 3 x^{2} - 2 h - 2 x + 5$

Step 2.2.3

Reorder $6 h x$ and $3 h^{2}$ .

$3 h^{2} + 6 h x + 3 x^{2} - 2 h - 2 x + 5$

Step 2.3

Find the components of the definition.

$f (x + h) = 3 h^{2} + 6 h x + 3 x^{2} - 2 h - 2 x + 5$

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

$f (x + h) = 3 h^{2} + 6 h x + 3 x^{2} - 2 h - 2 x + 5$

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

Step 3

Plug in the components.

$\frac{f (x + h) - f (x)}{h} = \frac{3 h^{2} + 6 h x + 3 x^{2} - 2 h - 2 x + 5 - (3 x^{2} - 2 x + 5)}{h}$

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.

$\frac{3 h^{2} + 6 h x + 3 x^{2} - 2 h - 2 x + 5 - (3 x^{2}) - (- 2 x) - 1 \cdot 5}{h}$

Step 4.1.2

Simplify.

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Step 4.1.2.1

Multiply $3$ by $- 1$ .

$\frac{3 h^{2} + 6 h x + 3 x^{2} - 2 h - 2 x + 5 - 3 x^{2} - (- 2 x) - 1 \cdot 5}{h}$

Step 4.1.2.2

Multiply $- 2$ by $- 1$ .

$\frac{3 h^{2} + 6 h x + 3 x^{2} - 2 h - 2 x + 5 - 3 x^{2} + 2 x - 1 \cdot 5}{h}$

Step 4.1.2.3

Multiply $- 1$ by $5$ .

$\frac{3 h^{2} + 6 h x + 3 x^{2} - 2 h - 2 x + 5 - 3 x^{2} + 2 x - 5}{h}$

Step 4.1.3

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

$\frac{3 h^{2} + 6 h x - 2 h - 2 x + 5 + 0 + 2 x - 5}{h}$

Step 4.1.4

Add $3 h^{2}$ and $0$ .

$\frac{3 h^{2} + 6 h x - 2 h - 2 x + 5 + 2 x - 5}{h}$

Step 4.1.5

Add $- 2 x$ and $2 x$ .

$\frac{3 h^{2} + 6 h x - 2 h + 0 + 5 - 5}{h}$

Step 4.1.6

Add $3 h^{2}$ and $0$ .

$\frac{3 h^{2} + 6 h x - 2 h + 5 - 5}{h}$

Step 4.1.7

Subtract $5$ from $5$ .

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

Step 4.1.8

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

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

Step 4.1.9

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

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Step 4.1.9.1

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

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

Step 4.1.9.2

Factor $h$ out of $6 h x$ .

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

Step 4.1.9.3

Factor $h$ out of $- 2 h$ .

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

Step 4.1.9.4

Factor $h$ out of $h (3 h) + h (6 x)$ .

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

Step 4.1.9.5

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

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

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.

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

Step 4.2.1.2

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

$3 h + 6 x - 2$

Step 4.2.2

Reorder $3 h$ and $6 x$ .

$6 x + 3 h - 2$

Step 5