[x+p]²-[x+q]²
=[(x+p)+(x+q)][(x+p)-(x+q)]
=(x+p+x+q)(x+p-x-q)
=(2x+p+q)(p-q)
【2x+y】²-【x+2y】²
=[(2x+y)+(x+2y)][(2x+y)-(x+2y)]
=(3x+3y)(x-y)
=3(x+y)(x-y)
16【x+y】²-9【x-y】²
=[4(x+y)]²-[3(x-y)]²
=[4(x+y)+3(x-y)][4(x+y)-3(x-y)]
=(7x+y)(x+7y)
4【2x-3】²-x²
=[2(2x-3)]²-x²
=[2(2x-3)+x][2(2x-3)-x]
=(5x-6)(3x-6)
=3(5x-6)(x-2)