(2y - x )² = (x-2y)²
So x(2y - x )² + 2x²(x - 2y)
= x(x-2y)² + 2x²( x - 2y )
= x(x-2y)[(x-2y) + 2x]
= x(x-2y)(3x-2y)
please check for mistakes.
but this is the key idea: (2y-x)²=(x-2y)².
