Question 263129
n to the second power + 11n +18

n^2 + 11n + 18

We want to find two factors in the form:

(n +- a)*(n +- b)

Since the sign on 18 is positive we know that the signs on the two factors are either both positive or both negative. a and b must be factors of 18 (i.e. 1, 18, 3, 6, 9, 2). We also know that a + b must be 11. Which two factors add up to 11?  +9 and +2.  So we have:

(n + 9)*(n + 2) = n^2 + 2n + 9n + 9*2 = n^2 +11n + 18