Factoring the square of 25X - the square of 10x [X-Y] + [X-Y]

Factoring the square of 25X - the square of 10x [X-Y] + [X-Y]

=25x^2-10x^2+10xy+x^2-2xy+y^2
=16x^2+8xy+y^2
=(4x+y)^2