(2a+b)^2-(2a+b)(2a-b)
=(2a+b)[(2a+b)-(2a-b) ]
=(2a+b)(2a+b-2a+b)
=2b(2a+b)
=4ab+2b^2
(2a+3b)^2(3b-2a)^2
=[(3b+2a)(3b-2a)]^2
=(9b^2-4a^2)^2
=81b^4+16a^4-72a^2b^2
(x-2y+3)(x+2y-3)
=[(x-(2y-3)][x+(2y-3)]
=x^2-(2y-3)^2
=x^2-4y^2+12y-9
4x^2+y^2=(2x-y)^2+4xy