[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=[...