# What is the answer for the 4th equation in question 3) ? http://postimg.org/image/behx7ffhr/

### 1 Answer | Add Yours

x^4 -5x^2 - 36

First, imagine the trinomial as...

x^2 - 5x - 36

Factor this equation.

You need to find two numbers whose sum is -5 and product is -36.

-9 + 4 = -5

-9 * 4 = -36

x^2 - 5x - 36

(x - 9)(x + 4)

Now change x to x^2 to get the original trinomial.**(x^2 - 9)(x^2 + 4)**

You can check your answer using FOIL.

(x^2 - 9)(x^2 + 4)

x^4 + 4x^2 - 9x^2 - 36

x^4 - 5x^2 - 36