Answer:
(x+4)(x-4)
Step-by-step explanation:
Here is a simple help for when you can take a square root of both terms:
(x+(squareroot)) x (x-(squareroot))
x times x = x^2
4 x -4 = -16
This is just a learned skill, most often from Alg 2, Alg 2 w/ trig, and Precal!
Hope this helps!
Is that a trick question wouldn't it be 20??? I'm confused