Question

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

Answer 1

`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)`