It seems that you have mistakenly typed the wrong equation which is supposed to be 4x^2 - 20x = 0.
So given the correct equation, the factor for this one would be this:
4x(x-5) = 0
So let us check.
4x (x) = 4x^2
4x (-5) = -20x
Which makes it 4x^2-20x = 0
I hope this answer helps.