We want to factor x²-11x+18
In order to factor it, we must find two numbers that add to -11 and multiply to 18.
We will go through the list of factors of 18:
1, 2, 3, 6, 9, 18
We see that 9 and 2 multiply to 18. But we want two numbers that add to -11, so we will simply put a negative sign in front of 9 and 2.
-9 and -2 still multiply to 18 and they add to -11, so now we can factor the expression:
x²-11x+18 = (x-2)(x-9)
