Precalculus Examples

$g (x) = \frac{x + 9}{x^{2} + 16}$

Step 1

Set the denominator in $\frac{x + 9}{x^{2} + 16}$ equal to $0$ to find where the expression is undefined.

$x^{2} + 16 = 0$

Step 2

Solve for $x$ .

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Step 2.1

Subtract $16$ from both sides of the equation.

$x^{2} = - 16$

Step 2.2

Take the specified root of both sides of the equation to eliminate the exponent on the left side.

$x = \pm \sqrt{- 16}$

Step 2.3

Simplify $\pm \sqrt{- 16}$ .

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Step 2.3.1

Rewrite $- 16$ as $- 1 (16)$ .

$x = \pm \sqrt{- 1 (16)}$

Step 2.3.2

Rewrite $\sqrt{- 1 (16)}$ as $\sqrt{- 1} \cdot \sqrt{16}$ .

$x = \pm \sqrt{- 1} \cdot \sqrt{16}$

Step 2.3.3

Rewrite $\sqrt{- 1}$ as $i$ .

$x = \pm i \cdot \sqrt{16}$

Step 2.3.4

Rewrite $16$ as $4^{2}$ .

$x = \pm i \cdot \sqrt{4^{2}}$

Step 2.3.5

Pull terms out from under the radical, assuming positive real numbers.

$x = \pm i \cdot 4$

Step 2.3.6

Move $4$ to the left of $i$ .

$x = \pm 4 i$

Step 2.4

The complete solution is the result of both the positive and negative portions of the solution.

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Step 2.4.1

First, use the positive value of the $\pm$ to find the first solution.

$x = 4 i$

Step 2.4.2

Next, use the negative value of the $\pm$ to find the second solution.

$x = - 4 i$

Step 2.4.3

The complete solution is the result of both the positive and negative portions of the solution.

$x = 4 i, - 4 i$

Step 3

The domain is all real numbers.

Interval Notation:

$(- \infty, \infty)$

Set-Builder Notation:

${x | x \in ℝ}$

Step 4