x^2 + 6x - 16 =0
The two numbers that satisfy the condition quadratics have is
1. They must add to 6
2, They must multiply to - 16
All quadratics have to satisfy these two things.
The only numbers that will are 8 and - 2
So the factors are
(x - 8)(x + 2) = 0
x - 8 = 0
x = 8
and
x + 2 = 0
x = - 2