How do you factor $a^2+11a+18$ ?

Question

5271 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2015-05-16T21:36:04

$a^2+11a+18 = (a+9)(a+2)$

To find this factorization, I noticed that $11 = 2+9$ and $18 = 2xx9$ .

This is an instance of the general observation that:

$(a+m)(a+n) = a^2 + (m+n)a + (mxxn)$

How do you factor a^2+11a+18a^2+11a+18?