(x+y)²-(x+m)²
=[(x+y)+(x+m)][(x+y)-(x+m)]
=(2x+y+m)(y-m)
16(a-b)²-9(a+b)²
=[4(a-b)+3(a+b)][4(a-b)-3(a+b)]
=(7a-b)(a-7b)
x²(y-8)+8²(8-y)
=x²(y-8)-8²(y-8)
=(y-8)(x+8)(x-8)
（x-1）（X+2）三次方-4（x-1）三次方（x+2）
=(x-1)(x+2)[(x+2)²-4(x-1)²]
=(x-1)(x+2)[(x+2)+2(x-1)][(x+2)-2(x-1)]
=3x(x-1)(x+2)(4-x)