Finite Math Examples

$y = \frac{x + 1}{x^{2} + 7 x - 12}$

Step 1

Set the denominator in $\frac{x + 1}{x^{2} + 7 x - 12}$ equal to $0$ to find where the expression is undefined.

$x^{2} + 7 x - 12 = 0$

Step 2

Solve for $x$ .

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Step 2.1

Use the quadratic formula to find the solutions.

$\frac{- b \pm \sqrt{b^{2} - 4 (a c)}}{2 a}$

Step 2.2

Substitute the values $a = 1$ , $b = 7$ , and $c = - 12$ into the quadratic formula and solve for $x$ .

$\frac{- 7 \pm \sqrt{7^{2} - 4 \cdot (1 \cdot - 12)}}{2 \cdot 1}$

Step 2.3

Simplify.

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Step 2.3.1

Simplify the numerator.

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Step 2.3.1.1

Raise $7$ to the power of $2$ .

$x = \frac{- 7 \pm \sqrt{49 - 4 \cdot 1 \cdot - 12}}{2 \cdot 1}$

Step 2.3.1.2

Multiply $- 4 \cdot 1 \cdot - 12$ .

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Step 2.3.1.2.1

Multiply $- 4$ by $1$ .

$x = \frac{- 7 \pm \sqrt{49 - 4 \cdot - 12}}{2 \cdot 1}$

Step 2.3.1.2.2

Multiply $- 4$ by $- 12$ .

$x = \frac{- 7 \pm \sqrt{49 + 48}}{2 \cdot 1}$

Step 2.3.1.3

Add $49$ and $48$ .

$x = \frac{- 7 \pm \sqrt{97}}{2 \cdot 1}$

Step 2.3.2

Multiply $2$ by $1$ .

$x = \frac{- 7 \pm \sqrt{97}}{2}$

Step 2.4

Simplify the expression to solve for the $+$ portion of the $\pm$ .

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Step 2.4.1

Simplify the numerator.

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Step 2.4.1.1

Raise $7$ to the power of $2$ .

$x = \frac{- 7 \pm \sqrt{49 - 4 \cdot 1 \cdot - 12}}{2 \cdot 1}$

Step 2.4.1.2

Multiply $- 4 \cdot 1 \cdot - 12$ .

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Step 2.4.1.2.1

Multiply $- 4$ by $1$ .

$x = \frac{- 7 \pm \sqrt{49 - 4 \cdot - 12}}{2 \cdot 1}$

Step 2.4.1.2.2

Multiply $- 4$ by $- 12$ .

$x = \frac{- 7 \pm \sqrt{49 + 48}}{2 \cdot 1}$

Step 2.4.1.3

Add $49$ and $48$ .

$x = \frac{- 7 \pm \sqrt{97}}{2 \cdot 1}$

Step 2.4.2

Multiply $2$ by $1$ .

$x = \frac{- 7 \pm \sqrt{97}}{2}$

Step 2.4.3

Change the $\pm$ to $+$ .

$x = \frac{- 7 + \sqrt{97}}{2}$

Step 2.4.4

Rewrite $- 7$ as $- 1 (7)$ .

$x = \frac{- 1 \cdot 7 + \sqrt{97}}{2}$

Step 2.4.5

Factor $- 1$ out of $\sqrt{97}$ .

$x = \frac{- 1 \cdot 7 - 1 (- \sqrt{97})}{2}$

Step 2.4.6

Factor $- 1$ out of $- 1 (7) - 1 (- \sqrt{97})$ .

$x = \frac{- 1 (7 - \sqrt{97})}{2}$

Step 2.4.7

Move the negative in front of the fraction.

$x = - \frac{7 - \sqrt{97}}{2}$

Step 2.5

Simplify the expression to solve for the $-$ portion of the $\pm$ .

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Step 2.5.1

Simplify the numerator.

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Step 2.5.1.1

Raise $7$ to the power of $2$ .

$x = \frac{- 7 \pm \sqrt{49 - 4 \cdot 1 \cdot - 12}}{2 \cdot 1}$

Step 2.5.1.2

Multiply $- 4 \cdot 1 \cdot - 12$ .

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Step 2.5.1.2.1

Multiply $- 4$ by $1$ .

$x = \frac{- 7 \pm \sqrt{49 - 4 \cdot - 12}}{2 \cdot 1}$

Step 2.5.1.2.2

Multiply $- 4$ by $- 12$ .

$x = \frac{- 7 \pm \sqrt{49 + 48}}{2 \cdot 1}$

Step 2.5.1.3

Add $49$ and $48$ .

$x = \frac{- 7 \pm \sqrt{97}}{2 \cdot 1}$

Step 2.5.2

Multiply $2$ by $1$ .

$x = \frac{- 7 \pm \sqrt{97}}{2}$

Step 2.5.3

Change the $\pm$ to $-$ .

$x = \frac{- 7 - \sqrt{97}}{2}$

Step 2.5.4

Rewrite $- 7$ as $- 1 (7)$ .

$x = \frac{- 1 \cdot 7 - \sqrt{97}}{2}$

Step 2.5.5

Factor $- 1$ out of $- \sqrt{97}$ .

$x = \frac{- 1 \cdot 7 - (\sqrt{97})}{2}$

Step 2.5.6

Factor $- 1$ out of $- 1 (7) - (\sqrt{97})$ .

$x = \frac{- 1 (7 + \sqrt{97})}{2}$

Step 2.5.7

Move the negative in front of the fraction.

$x = - \frac{7 + \sqrt{97}}{2}$

Step 2.6

The final answer is the combination of both solutions.

$x = - \frac{7 - \sqrt{97}}{2}, - \frac{7 + \sqrt{97}}{2}$

Step 3

The domain is all values of $x$ that make the expression defined.

Interval Notation:

$(- \infty, - \frac{7 + \sqrt{97}}{2}) \cup (- \frac{7 + \sqrt{97}}{2}, - \frac{7 - \sqrt{97}}{2}) \cup (- \frac{7 - \sqrt{97}}{2}, \infty)$

Set-Builder Notation:

${x | x \neq - \frac{7 - \sqrt{97}}{2}, - \frac{7 + \sqrt{97}}{2}}$

Step 4