Precalculus Examples

$f (x) = x^{\frac{3}{2}}$

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.

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

Step 2.1.2

The final answer is ${(x + h)}^{\frac{3}{2}}$ .

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

Step 2.2

Find the components of the definition.

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

$f (x) = x^{\frac{3}{2}}$

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

$f (x) = x^{\frac{3}{2}}$

Step 3

Plug in the components.

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

Step 4

Simplify the numerator.

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Step 4.1

Rewrite ${(x + h)}^{\frac{3}{2}}$ as ${({(x + h)}^{\frac{1}{2}})}^{3}$ .

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

Step 4.2

Rewrite $x^{\frac{3}{2}}$ as ${(x^{\frac{1}{2}})}^{3}$ .

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

Step 4.3

Since both terms are perfect cubes, factor using the difference of cubes formula, $a^{3} - b^{3} = (a - b) (a^{2} + a b + b^{2})$ where $a = {(x + h)}^{\frac{1}{2}}$ and $b = x^{\frac{1}{2}}$ .

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

Step 4.4

Simplify.

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Step 4.4.1

Multiply the exponents in ${({(x + h)}^{\frac{1}{2}})}^{2}$ .

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Step 4.4.1.1

Apply the power rule and multiply exponents, ${(a^{m})}^{n} = a^{m n}$ .

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

Step 4.4.1.2

Cancel the common factor of $2$ .

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Step 4.4.1.2.1

Cancel the common factor.

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

Step 4.4.1.2.2

Rewrite the expression.

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

Step 4.4.2

Simplify.

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

Step 4.4.3

Multiply the exponents in ${(x^{\frac{1}{2}})}^{2}$ .

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Step 4.4.3.1

Apply the power rule and multiply exponents, ${(a^{m})}^{n} = a^{m n}$ .

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

Step 4.4.3.2

Cancel the common factor of $2$ .

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Step 4.4.3.2.1

Cancel the common factor.

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

Step 4.4.3.2.2

Rewrite the expression.

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

Step 4.4.4

Simplify.

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

Step 4.4.5

Add $x$ and $x$ .

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

Step 5