Precalculus Examples

$f (x) = \frac{2 x - 1}{3 x + 5}$

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.

$f (x + h) = \frac{2 (x + h) - 1}{3 (x + h) + 5}$

Step 2.1.2

Simplify the result.

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Step 2.1.2.1

Apply the distributive property.

$f (x + h) = \frac{2 x + 2 h - 1}{3 (x + h) + 5}$

Step 2.1.2.2

Apply the distributive property.

$f (x + h) = \frac{2 x + 2 h - 1}{3 x + 3 h + 5}$

Step 2.1.2.3

The final answer is $\frac{2 x + 2 h - 1}{3 x + 3 h + 5}$ .

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

Step 2.2

Find the components of the definition.

$f (x + h) = \frac{2 x + 2 h - 1}{3 x + 3 h + 5}$

$f (x) = \frac{2 x - 1}{3 x + 5}$

$f (x + h) = \frac{2 x + 2 h - 1}{3 x + 3 h + 5}$

$f (x) = \frac{2 x - 1}{3 x + 5}$

Step 3

Plug in the components.

$\frac{f (x + h) - f (x)}{h} = \frac{\frac{2 x + 2 h - 1}{3 x + 3 h + 5} - (\frac{2 x - 1}{3 x + 5})}{h}$

Step 4

Simplify.

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Step 4.1

Simplify the numerator.

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Step 4.1.1

To write $\frac{2 x + 2 h - 1}{3 x + 3 h + 5}$ as a fraction with a common denominator, multiply by $\frac{3 x + 5}{3 x + 5}$ .

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

Step 4.1.2

To write $- \frac{2 x - 1}{3 x + 5}$ as a fraction with a common denominator, multiply by $\frac{3 x + 3 h + 5}{3 x + 3 h + 5}$ .

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

Step 4.1.3

Write each expression with a common denominator of $(3 x + 3 h + 5) (3 x + 5)$ , by multiplying each by an appropriate factor of $1$ .

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Step 4.1.3.1

Multiply $\frac{2 x + 2 h - 1}{3 x + 3 h + 5}$ by $\frac{3 x + 5}{3 x + 5}$ .

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

Step 4.1.3.2

Multiply $\frac{2 x - 1}{3 x + 5}$ by $\frac{3 x + 3 h + 5}{3 x + 3 h + 5}$ .

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

Step 4.1.3.3

Reorder the factors of $(3 x + 5) (3 x + 3 h + 5)$ .

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

Step 4.1.4

Combine the numerators over the common denominator.

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

Step 4.1.5

Rewrite $\frac{(2 x + 2 h - 1) (3 x + 5) - (2 x - 1) (3 x + 3 h + 5)}{(3 x + 3 h + 5) (3 x + 5)}$ in a factored form.

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Step 4.1.5.1

Expand $(2 x + 2 h - 1) (3 x + 5)$ by multiplying each term in the first expression by each term in the second expression.

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

Step 4.1.5.2

Simplify each term.

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Step 4.1.5.2.1

Rewrite using the commutative property of multiplication.

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

Step 4.1.5.2.2

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

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Step 4.1.5.2.2.1

Move $x$ .

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

Step 4.1.5.2.2.2

Multiply $x$ by $x$ .

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

Step 4.1.5.2.3

Multiply $2$ by $3$ .

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

Step 4.1.5.2.4

Multiply $5$ by $2$ .

$\frac{\frac{6 x^{2} + 10 x + 2 h (3 x) + 2 h \cdot 5 - 1 (3 x) - 1 \cdot 5 - (2 x - 1) (3 x + 3 h + 5)}{(3 x + 3 h + 5) (3 x + 5)}}{h}$

Step 4.1.5.2.5

Rewrite using the commutative property of multiplication.

$\frac{\frac{6 x^{2} + 10 x + 2 \cdot 3 h x + 2 h \cdot 5 - 1 (3 x) - 1 \cdot 5 - (2 x - 1) (3 x + 3 h + 5)}{(3 x + 3 h + 5) (3 x + 5)}}{h}$

Step 4.1.5.2.6

Multiply $2$ by $3$ .

$\frac{\frac{6 x^{2} + 10 x + 6 h x + 2 h \cdot 5 - 1 (3 x) - 1 \cdot 5 - (2 x - 1) (3 x + 3 h + 5)}{(3 x + 3 h + 5) (3 x + 5)}}{h}$

Step 4.1.5.2.7

Multiply $5$ by $2$ .

$\frac{\frac{6 x^{2} + 10 x + 6 h x + 10 h - 1 (3 x) - 1 \cdot 5 - (2 x - 1) (3 x + 3 h + 5)}{(3 x + 3 h + 5) (3 x + 5)}}{h}$

Step 4.1.5.2.8

Multiply $3$ by $- 1$ .

$\frac{\frac{6 x^{2} + 10 x + 6 h x + 10 h - 3 x - 1 \cdot 5 - (2 x - 1) (3 x + 3 h + 5)}{(3 x + 3 h + 5) (3 x + 5)}}{h}$

Step 4.1.5.2.9

Multiply $- 1$ by $5$ .

$\frac{\frac{6 x^{2} + 10 x + 6 h x + 10 h - 3 x - 5 - (2 x - 1) (3 x + 3 h + 5)}{(3 x + 3 h + 5) (3 x + 5)}}{h}$

Step 4.1.5.3

Subtract $3 x$ from $10 x$ .

$\frac{\frac{6 x^{2} + 7 x + 6 h x + 10 h - 5 - (2 x - 1) (3 x + 3 h + 5)}{(3 x + 3 h + 5) (3 x + 5)}}{h}$

Step 4.1.5.4

Apply the distributive property.

$\frac{\frac{6 x^{2} + 7 x + 6 h x + 10 h - 5 + (- (2 x) - - 1) (3 x + 3 h + 5)}{(3 x + 3 h + 5) (3 x + 5)}}{h}$

Step 4.1.5.5

Multiply $2$ by $- 1$ .

$\frac{\frac{6 x^{2} + 7 x + 6 h x + 10 h - 5 + (- 2 x - - 1) (3 x + 3 h + 5)}{(3 x + 3 h + 5) (3 x + 5)}}{h}$

Step 4.1.5.6

Multiply $- 1$ by $- 1$ .

$\frac{\frac{6 x^{2} + 7 x + 6 h x + 10 h - 5 + (- 2 x + 1) (3 x + 3 h + 5)}{(3 x + 3 h + 5) (3 x + 5)}}{h}$

Step 4.1.5.7

Expand $(- 2 x + 1) (3 x + 3 h + 5)$ by multiplying each term in the first expression by each term in the second expression.

$\frac{\frac{6 x^{2} + 7 x + 6 h x + 10 h - 5 - 2 x (3 x) - 2 x (3 h) - 2 x \cdot 5 + 1 (3 x) + 1 (3 h) + 1 \cdot 5}{(3 x + 3 h + 5) (3 x + 5)}}{h}$

Step 4.1.5.8

Simplify each term.

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Step 4.1.5.8.1

Rewrite using the commutative property of multiplication.

$\frac{\frac{6 x^{2} + 7 x + 6 h x + 10 h - 5 - 2 \cdot 3 x \cdot x - 2 x (3 h) - 2 x \cdot 5 + 1 (3 x) + 1 (3 h) + 1 \cdot 5}{(3 x + 3 h + 5) (3 x + 5)}}{h}$

Step 4.1.5.8.2

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

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Step 4.1.5.8.2.1

Move $x$ .

$\frac{\frac{6 x^{2} + 7 x + 6 h x + 10 h - 5 - 2 \cdot 3 (x \cdot x) - 2 x (3 h) - 2 x \cdot 5 + 1 (3 x) + 1 (3 h) + 1 \cdot 5}{(3 x + 3 h + 5) (3 x + 5)}}{h}$

Step 4.1.5.8.2.2

Multiply $x$ by $x$ .

$\frac{\frac{6 x^{2} + 7 x + 6 h x + 10 h - 5 - 2 \cdot 3 x^{2} - 2 x (3 h) - 2 x \cdot 5 + 1 (3 x) + 1 (3 h) + 1 \cdot 5}{(3 x + 3 h + 5) (3 x + 5)}}{h}$

Step 4.1.5.8.3

Multiply $- 2$ by $3$ .

$\frac{\frac{6 x^{2} + 7 x + 6 h x + 10 h - 5 - 6 x^{2} - 2 x (3 h) - 2 x \cdot 5 + 1 (3 x) + 1 (3 h) + 1 \cdot 5}{(3 x + 3 h + 5) (3 x + 5)}}{h}$

Step 4.1.5.8.4

Rewrite using the commutative property of multiplication.

$\frac{\frac{6 x^{2} + 7 x + 6 h x + 10 h - 5 - 6 x^{2} - 2 \cdot 3 x h - 2 x \cdot 5 + 1 (3 x) + 1 (3 h) + 1 \cdot 5}{(3 x + 3 h + 5) (3 x + 5)}}{h}$

Step 4.1.5.8.5

Multiply $- 2$ by $3$ .

$\frac{\frac{6 x^{2} + 7 x + 6 h x + 10 h - 5 - 6 x^{2} - 6 x h - 2 x \cdot 5 + 1 (3 x) + 1 (3 h) + 1 \cdot 5}{(3 x + 3 h + 5) (3 x + 5)}}{h}$

Step 4.1.5.8.6

Multiply $5$ by $- 2$ .

$\frac{\frac{6 x^{2} + 7 x + 6 h x + 10 h - 5 - 6 x^{2} - 6 x h - 10 x + 1 (3 x) + 1 (3 h) + 1 \cdot 5}{(3 x + 3 h + 5) (3 x + 5)}}{h}$

Step 4.1.5.8.7

Multiply $3 x$ by $1$ .

$\frac{\frac{6 x^{2} + 7 x + 6 h x + 10 h - 5 - 6 x^{2} - 6 x h - 10 x + 3 x + 1 (3 h) + 1 \cdot 5}{(3 x + 3 h + 5) (3 x + 5)}}{h}$

Step 4.1.5.8.8

Multiply $3 h$ by $1$ .

$\frac{\frac{6 x^{2} + 7 x + 6 h x + 10 h - 5 - 6 x^{2} - 6 x h - 10 x + 3 x + 3 h + 1 \cdot 5}{(3 x + 3 h + 5) (3 x + 5)}}{h}$

Step 4.1.5.8.9

Multiply $5$ by $1$ .

$\frac{\frac{6 x^{2} + 7 x + 6 h x + 10 h - 5 - 6 x^{2} - 6 x h - 10 x + 3 x + 3 h + 5}{(3 x + 3 h + 5) (3 x + 5)}}{h}$

Step 4.1.5.9

Add $- 10 x$ and $3 x$ .

$\frac{\frac{6 x^{2} + 7 x + 6 h x + 10 h - 5 - 6 x^{2} - 6 x h - 7 x + 3 h + 5}{(3 x + 3 h + 5) (3 x + 5)}}{h}$

Step 4.1.5.10

Subtract $6 x^{2}$ from $6 x^{2}$ .

$\frac{\frac{7 x + 6 h x + 10 h - 5 + 0 - 6 x h - 7 x + 3 h + 5}{(3 x + 3 h + 5) (3 x + 5)}}{h}$

Step 4.1.5.11

Add $7 x$ and $0$ .

$\frac{\frac{7 x + 6 h x + 10 h - 5 - 6 x h - 7 x + 3 h + 5}{(3 x + 3 h + 5) (3 x + 5)}}{h}$

Step 4.1.5.12

Subtract $7 x$ from $7 x$ .

$\frac{\frac{6 h x + 10 h - 5 - 6 x h + 0 + 3 h + 5}{(3 x + 3 h + 5) (3 x + 5)}}{h}$

Step 4.1.5.13

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

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Step 4.1.5.13.1

Move $h$ .

$\frac{\frac{10 h - 5 + 6 x h - 6 x h + 0 + 3 h + 5}{(3 x + 3 h + 5) (3 x + 5)}}{h}$

Step 4.1.5.13.2

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

$\frac{\frac{10 h - 5 + 0 + 0 + 3 h + 5}{(3 x + 3 h + 5) (3 x + 5)}}{h}$

Step 4.1.5.14

Add $10 h$ and $0$ .

$\frac{\frac{10 h - 5 + 0 + 3 h + 5}{(3 x + 3 h + 5) (3 x + 5)}}{h}$

Step 4.1.5.15

Add $10 h$ and $0$ .

$\frac{\frac{10 h - 5 + 3 h + 5}{(3 x + 3 h + 5) (3 x + 5)}}{h}$

Step 4.1.5.16

Add $10 h$ and $3 h$ .

$\frac{\frac{13 h - 5 + 5}{(3 x + 3 h + 5) (3 x + 5)}}{h}$

Step 4.1.5.17

Add $- 5$ and $5$ .

$\frac{\frac{13 h + 0}{(3 x + 3 h + 5) (3 x + 5)}}{h}$

Step 4.1.5.18

Add $13 h$ and $0$ .

$\frac{\frac{13 h}{(3 x + 3 h + 5) (3 x + 5)}}{h}$

Step 4.2

Multiply the numerator by the reciprocal of the denominator.

$\frac{13 h}{(3 x + 3 h + 5) (3 x + 5)} \cdot \frac{1}{h}$

Step 4.3

Cancel the common factor of $h$ .

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Step 4.3.1

Factor $h$ out of $13 h$ .

$\frac{h \cdot 13}{(3 x + 3 h + 5) (3 x + 5)} \cdot \frac{1}{h}$

Step 4.3.2

Cancel the common factor.

$\frac{h \cdot 13}{(3 x + 3 h + 5) (3 x + 5)} \cdot \frac{1}{h}$

Step 4.3.3

Rewrite the expression.

$\frac{13}{(3 x + 3 h + 5) (3 x + 5)}$

Step 5