(2x+3y)^2-(3x-2y)^2
=[(2x+3y)-(3x-2y)][(2x+3y)+(3x-2y)]
=(2x+3y-3x+2y)(2x+3y+3x-2y)
=(-x+5y)(5x+y)
=-(x-5y)(5x+y)