Set up your parentheses, and put x in the front of both because x is squared. It should look like this: (x )(x ). Next, you find notice that one sign must be positive, and one must be negative. Then, you find the factors of 36. 6 and 6, 3 and 12, 1 and 36, 18 and 2, and 9 and 4. You then guess and check with the different signs and factors what will get you back to the trinomial using the FOIL method. When you do this, you should get (x-9)(x+4).
