① (a-b)^2*(m+n)-(-m-n)(b-a)
=(m+n)(a-b)(a-b-1)
② 16(x+y)^2-25(x-y)^2
=[4(x+y)+5(x-y)][4(x+y)-5(x-y)]
=(9x-y)(9y-x)
③16(a+b)^2-9(a-b)^2=【4(a+b)+3(a-b)】【4(a+b)-3(a-b)】
=(7a-b)(a+7b)
④9m^2(a-b)^3+49(b-a)^3
=(a-b)^3(3m+7)(3m-7)
⑤(x+y-z)^2-(x-y+z)^2=2x(2y-2z)
⑥(a^2-b^2)+(3a-3b)=(a-b)(a+b+3)
⑦x^4-1=(x²+1)(x²-1)= x²+1)(x+1)(x-1)