factorize completely the expression 4x^2-8xy+16y^2

Answer 1

note that the first and last terms are perfect squares. So, try
(2x-4y)^2 = 4x^2 - 16xy + 16y^2
so, that's no good. so I guess all you can do is factor out the 4.
4(x^2 - 2xy + 4y^2)
If you want to factor that quadratic, you'll need the quadratic formula and complex roots.