Find Where Undefined/Discontinuous f(x)=(2x+10)/(x^2+9x+20)

$f (x) = \frac{2 x + 10}{x^{2} + 9 x + 20}$

Step 1

Set the denominator in $\frac{2 x + 10}{x^{2} + 9 x + 20}$ equal to $0$ to find where the expression is undefined.

$x^{2} + 9 x + 20 = 0$

Step 2

Solve for $x$ .

Factor $x^{2} + 9 x + 20$ 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 $20$ and whose sum is $9$ .

$4, 5$

Write the factored form using these integers.

$(x + 4) (x + 5) = 0$

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

$x + 4 = 0$

$x + 5 = 0$

Set $x + 4$ equal to $0$ and solve for $x$ .

Set $x + 4$ equal to $0$ .

$x + 4 = 0$

Subtract $4$ from both sides of the equation.

$x = - 4$

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

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

$x + 5 = 0$

Subtract $5$ from both sides of the equation.

$x = - 5$

The final solution is all the values that make $(x + 4) (x + 5) = 0$ true.

$x = - 4, - 5$

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 $0$ .

$x = - 5, x = - 4$

Step 4

Find Where Undefined/Discontinuous f(x)=(2x+10)/(x^2+9x+20)

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