In order to factorize the given expression, we find to find two numbers p and q such that:
p + q = 14, pq = 45
Clearly,
5 + 9 = 14, 5 (9) = 45
Therefore, split 14x as 5x + 9x
Therefore,
x2 + 14x + 45 = x2 + 5x + 9x + 45
= x (x + 5) – 9 (x + 5)
= (x + 9) (x + 5)