Precalculus Examples

$f (x) = \frac{24}{1 + 3 e^{- 1.3 x}}$

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.

$f (x + h) = \frac{24}{1 + 3 e^{- 1.3 (x + h)}}$

Step 2.1.2

Simplify the result.

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Step 2.1.2.1

Apply the distributive property.

$f (x + h) = \frac{24}{1 + 3 e^{- 1.3 x - 1.3 h}}$

Step 2.1.2.2

The final answer is $\frac{24}{1 + 3 e^{- 1.3 x - 1.3 h}}$ .

$\frac{24}{1 + 3 e^{- 1.3 x - 1.3 h}}$

Step 2.2

Find the components of the definition.

$f (x + h) = \frac{24}{1 + 3 e^{- 1.3 x - 1.3 h}}$

$f (x) = \frac{24}{1 + 3 e^{- 1.3 x}}$

$f (x + h) = \frac{24}{1 + 3 e^{- 1.3 x - 1.3 h}}$

$f (x) = \frac{24}{1 + 3 e^{- 1.3 x}}$

Step 3

Plug in the components.

$\frac{f (x + h) - f (x)}{h} = \frac{\frac{24}{1 + 3 e^{- 1.3 x - 1.3 h}} - (\frac{24}{1 + 3 e^{- 1.3 x}})}{h}$

Step 4

Simplify.

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Step 4.1

Simplify the numerator.

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Step 4.1.1

To write $\frac{24}{1 + 3 e^{- 1.3 x - 1.3 h}}$ as a fraction with a common denominator, multiply by $\frac{1 + 3 e^{- 1.3 x}}{1 + 3 e^{- 1.3 x}}$ .

$\frac{\frac{24}{1 + 3 e^{- 1.3 x - 1.3 h}} \cdot \frac{1 + 3 e^{- 1.3 x}}{1 + 3 e^{- 1.3 x}} - \frac{24}{1 + 3 e^{- 1.3 x}}}{h}$

Step 4.1.2

To write $- \frac{24}{1 + 3 e^{- 1.3 x}}$ as a fraction with a common denominator, multiply by $\frac{1 + 3 e^{- 1.3 x - 1.3 h}}{1 + 3 e^{- 1.3 x - 1.3 h}}$ .

$\frac{\frac{24}{1 + 3 e^{- 1.3 x - 1.3 h}} \cdot \frac{1 + 3 e^{- 1.3 x}}{1 + 3 e^{- 1.3 x}} - \frac{24}{1 + 3 e^{- 1.3 x}} \cdot \frac{1 + 3 e^{- 1.3 x - 1.3 h}}{1 + 3 e^{- 1.3 x - 1.3 h}}}{h}$

Step 4.1.3

Write each expression with a common denominator of $(1 + 3 e^{- 1.3 x - 1.3 h}) (1 + 3 e^{- 1.3 x})$ , by multiplying each by an appropriate factor of $1$ .

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Step 4.1.3.1

Multiply $\frac{24}{1 + 3 e^{- 1.3 x - 1.3 h}}$ by $\frac{1 + 3 e^{- 1.3 x}}{1 + 3 e^{- 1.3 x}}$ .

$\frac{\frac{24 (1 + 3 e^{- 1.3 x})}{(1 + 3 e^{- 1.3 x - 1.3 h}) (1 + 3 e^{- 1.3 x})} - \frac{24}{1 + 3 e^{- 1.3 x}} \cdot \frac{1 + 3 e^{- 1.3 x - 1.3 h}}{1 + 3 e^{- 1.3 x - 1.3 h}}}{h}$

Step 4.1.3.2

Multiply $\frac{24}{1 + 3 e^{- 1.3 x}}$ by $\frac{1 + 3 e^{- 1.3 x - 1.3 h}}{1 + 3 e^{- 1.3 x - 1.3 h}}$ .

$\frac{\frac{24 (1 + 3 e^{- 1.3 x})}{(1 + 3 e^{- 1.3 x - 1.3 h}) (1 + 3 e^{- 1.3 x})} - \frac{24 (1 + 3 e^{- 1.3 x - 1.3 h})}{(1 + 3 e^{- 1.3 x}) (1 + 3 e^{- 1.3 x - 1.3 h})}}{h}$

Step 4.1.3.3

Reorder the factors of $(1 + 3 e^{- 1.3 x}) (1 + 3 e^{- 1.3 x - 1.3 h})$ .

$\frac{\frac{24 (1 + 3 e^{- 1.3 x})}{(1 + 3 e^{- 1.3 x - 1.3 h}) (1 + 3 e^{- 1.3 x})} - \frac{24 (1 + 3 e^{- 1.3 x - 1.3 h})}{(1 + 3 e^{- 1.3 x - 1.3 h}) (1 + 3 e^{- 1.3 x})}}{h}$

Step 4.1.4

Combine the numerators over the common denominator.

$\frac{\frac{24 (1 + 3 e^{- 1.3 x}) - 24 (1 + 3 e^{- 1.3 x - 1.3 h})}{(1 + 3 e^{- 1.3 x - 1.3 h}) (1 + 3 e^{- 1.3 x})}}{h}$

Step 4.1.5

Rewrite $\frac{24 (1 + 3 e^{- 1.3 x}) - 24 (1 + 3 e^{- 1.3 x - 1.3 h})}{(1 + 3 e^{- 1.3 x - 1.3 h}) (1 + 3 e^{- 1.3 x})}$ in a factored form.

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Step 4.1.5.1

Factor $24$ out of $24 (1 + 3 e^{- 1.3 x}) - 24 (1 + 3 e^{- 1.3 x - 1.3 h})$ .

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Step 4.1.5.1.1

Factor $24$ out of $- 24 (1 + 3 e^{- 1.3 x - 1.3 h})$ .

$\frac{\frac{24 (1 + 3 e^{- 1.3 x}) + 24 (- (1 + 3 e^{- 1.3 x - 1.3 h}))}{(1 + 3 e^{- 1.3 x - 1.3 h}) (1 + 3 e^{- 1.3 x})}}{h}$

Step 4.1.5.1.2

Factor $24$ out of $24 (1 + 3 e^{- 1.3 x}) + 24 (- (1 + 3 e^{- 1.3 x - 1.3 h}))$ .

$\frac{\frac{24 (1 + 3 e^{- 1.3 x} - (1 + 3 e^{- 1.3 x - 1.3 h}))}{(1 + 3 e^{- 1.3 x - 1.3 h}) (1 + 3 e^{- 1.3 x})}}{h}$

Step 4.1.5.2

Apply the distributive property.

$\frac{\frac{24 (1 + 3 e^{- 1.3 x} - 1 \cdot 1 - (3 e^{- 1.3 x - 1.3 h}))}{(1 + 3 e^{- 1.3 x - 1.3 h}) (1 + 3 e^{- 1.3 x})}}{h}$

Step 4.1.5.3

Multiply $- 1$ by $1$ .

$\frac{\frac{24 (1 + 3 e^{- 1.3 x} - 1 - (3 e^{- 1.3 x - 1.3 h}))}{(1 + 3 e^{- 1.3 x - 1.3 h}) (1 + 3 e^{- 1.3 x})}}{h}$

Step 4.1.5.4

Multiply $3$ by $- 1$ .

$\frac{\frac{24 (1 + 3 e^{- 1.3 x} - 1 - 3 e^{- 1.3 x - 1.3 h})}{(1 + 3 e^{- 1.3 x - 1.3 h}) (1 + 3 e^{- 1.3 x})}}{h}$

Step 4.1.5.5

Subtract $1$ from $1$ .

$\frac{\frac{24 (3 e^{- 1.3 x} + 0 - 3 e^{- 1.3 x - 1.3 h})}{(1 + 3 e^{- 1.3 x - 1.3 h}) (1 + 3 e^{- 1.3 x})}}{h}$

Step 4.1.5.6

Add $3 e^{- 1.3 x}$ and $0$ .

$\frac{\frac{24 (3 e^{- 1.3 x} - 3 e^{- 1.3 x - 1.3 h})}{(1 + 3 e^{- 1.3 x - 1.3 h}) (1 + 3 e^{- 1.3 x})}}{h}$

Step 4.1.5.7

Factor $3$ out of $3 e^{- 1.3 x} - 3 e^{- 1.3 x - 1.3 h}$ .

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Step 4.1.5.7.1

Factor $3$ out of $3 e^{- 1.3 x}$ .

$\frac{\frac{24 (3 (e^{- 1.3 x}) - 3 e^{- 1.3 x - 1.3 h})}{(1 + 3 e^{- 1.3 x - 1.3 h}) (1 + 3 e^{- 1.3 x})}}{h}$

Step 4.1.5.7.2

Factor $3$ out of $- 3 e^{- 1.3 x - 1.3 h}$ .

$\frac{\frac{24 (3 (e^{- 1.3 x}) + 3 (- e^{- 1.3 x - 1.3 h}))}{(1 + 3 e^{- 1.3 x - 1.3 h}) (1 + 3 e^{- 1.3 x})}}{h}$

Step 4.1.5.7.3

Factor $3$ out of $3 (e^{- 1.3 x}) + 3 (- e^{- 1.3 x - 1.3 h})$ .

$\frac{\frac{24 (3 (e^{- 1.3 x} - e^{- 1.3 x - 1.3 h}))}{(1 + 3 e^{- 1.3 x - 1.3 h}) (1 + 3 e^{- 1.3 x})}}{h}$

$\frac{\frac{24 \cdot 3 (e^{- 1.3 x} - e^{- 1.3 x - 1.3 h})}{(1 + 3 e^{- 1.3 x - 1.3 h}) (1 + 3 e^{- 1.3 x})}}{h}$

Step 4.1.5.8

Multiply $24$ by $3$ .

$\frac{\frac{72 (e^{- 1.3 x} - e^{- 1.3 x - 1.3 h})}{(1 + 3 e^{- 1.3 x - 1.3 h}) (1 + 3 e^{- 1.3 x})}}{h}$

Step 4.2

Multiply the numerator by the reciprocal of the denominator.

$\frac{72 (e^{- 1.3 x} - e^{- 1.3 x - 1.3 h})}{(1 + 3 e^{- 1.3 x - 1.3 h}) (1 + 3 e^{- 1.3 x})} \cdot \frac{1}{h}$

Step 4.3

Combine.

$\frac{72 (e^{- 1.3 x} - e^{- 1.3 x - 1.3 h}) \cdot 1}{(1 + 3 e^{- 1.3 x - 1.3 h}) (1 + 3 e^{- 1.3 x}) h}$

Step 4.4

Simplify the expression.

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Step 4.4.1

Multiply $72$ by $1$ .

$\frac{72 (e^{- 1.3 x} - e^{- 1.3 x - 1.3 h})}{(1 + 3 e^{- 1.3 x - 1.3 h}) (1 + 3 e^{- 1.3 x}) h}$

Step 4.4.2

Reorder factors in $\frac{72 (e^{- 1.3 x} - e^{- 1.3 x - 1.3 h})}{(1 + 3 e^{- 1.3 x - 1.3 h}) (1 + 3 e^{- 1.3 x}) h}$ .

$\frac{72 (e^{- 1.3 x} - e^{- 1.3 x - 1.3 h})}{h (1 + 3 e^{- 1.3 x - 1.3 h}) (1 + 3 e^{- 1.3 x})}$

Step 5