Find the Excluded Values (x^2+x-90)/(x^2+2x-80)

$\frac{x^{2} + x - 90}{x^{2} + 2 x - 80}$

Step 1

Set the denominator in $\frac{x^{2} + x - 90}{x^{2} + 2 x - 80}$ equal to $0$ to find where the expression is undefined.

$x^{2} + 2 x - 80 = 0$

Step 2

Solve for $x$ .

Factor $x^{2} + 2 x - 80$ using the AC method.

Consider the form $x^{2} + b x + c$ . Find a pair of integers whose product is $c$ and whose sum is $b$ . In this case, whose product is $- 80$ and whose sum is $2$ .

$- 8, 10$

Write the factored form using these integers.

$(x - 8) (x + 10) = 0$

If any individual factor on the left side of the equation is equal to $0$ , the entire expression will be equal to $0$ .

$x - 8 = 0$

$x + 10 = 0$

Set $x - 8$ equal to $0$ and solve for $x$ .

Set $x - 8$ equal to $0$ .

$x - 8 = 0$

Add $8$ to both sides of the equation.

$x = 8$

Set $x + 10$ equal to $0$ and solve for $x$ .

Set $x + 10$ equal to $0$ .

$x + 10 = 0$

Subtract $10$ from both sides of the equation.

$x = - 10$

The final solution is all the values that make $(x - 8) (x + 10) = 0$ true.

$x = 8, - 10$

Step 3

The equation is undefined where the denominator equals $0$ , the argument of a square root is less than $0$ , or the argument of a logarithm is less than or equal to $0$ .

$x = - 10, x = 8$

Step 4

Find the Excluded Values (x^2+x-90)/(x^2+2x-80)

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