Find the Excluded Values ((x^2-13x+40)/(x^2-2x-15))÷(x^2-5x-24)

$\frac{x^{2} - 13 x + 40}{x^{2} - 2 x - 15} \div (x^{2} - 5 x - 24)$

Step 1

Set the denominator in $\frac{x^{2} - 13 x + 40}{x^{2} - 2 x - 15}$ equal to $0$ to find where the expression is undefined.

$x^{2} - 2 x - 15 = 0$

Step 2

Solve for $x$ .

Factor $x^{2} - 2 x - 15$ 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 $- 15$ and whose sum is $- 2$ .

$- 5, 3$

Write the factored form using these integers.

$(x - 5) (x + 3) = 0$

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

$x - 5 = 0$

$x + 3 = 0$

Set $x - 5$ equal to $0$ and solve for $x$ .

Set $x - 5$ equal to $0$ .

$x - 5 = 0$

Add $5$ to both sides of the equation.

$x = 5$

Set $x + 3$ equal to $0$ and solve for $x$ .

Set $x + 3$ equal to $0$ .

$x + 3 = 0$

Subtract $3$ from both sides of the equation.

$x = - 3$

The final solution is all the values that make $(x - 5) (x + 3) = 0$ true.

$x = 5, - 3$

Step 3

Set the denominator in $\frac{\frac{x^{2} - 13 x + 40}{x^{2} - 2 x - 15}}{x^{2} - 5 x - 24}$ equal to $0$ to find where the expression is undefined.

$x^{2} - 5 x - 24 = 0$

Step 4

Solve for $x$ .

Factor $x^{2} - 5 x - 24$ 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 $- 24$ and whose sum is $- 5$ .

$- 8, 3$

Write the factored form using these integers.

$(x - 8) (x + 3) = 0$

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

$x - 8 = 0$

$x + 3 = 0$

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 $x + 3$ equal to $0$ and solve for $x$ .

Set $x + 3$ equal to $0$ .

$x + 3 = 0$

Subtract $3$ from both sides of the equation.

$x = - 3$

The final solution is all the values that make $(x - 8) (x + 3) = 0$ true.

$x = 8, - 3$

Step 5

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 $0$ .

$x = - 3, x = 5, x = 8$

Step 6

Find the Excluded Values ((x^2-13x+40)/(x^2-2x-15))÷(x^2-5x-24)

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