Question

Simplify:
(4x-y)(4x+y)

Answer 1

You need to foil.

F = 4x * 4x = 16x^2
O = 4x* y = 4xy
I = -y * 4x = -4xy
L = -y * y = -y^2

Add like terms and you get 16x^2 - y^2

Hint... if you have the exact same first terms and last terms...
(4x y)(4x y) and you have one + sign and one - sign you can get the answer by multiplying the F and the L only because the O and I will ALWAYS cancel out.

Be careful though, you can only do that when they are identical with one + sign and one - sign.

Answer 2

ok thanks