10个平方差公式,10点以前要16a²b-9m² 1.96x²-y² 25/81

(4a √ b+3m)(4a √ b-3m) (1.6x+y)(1.6x-y) ( 5/9x+3/4y)(5/9x-3/4y)
(√j+16m)(√j-16m) (1/8x+1)(1/8x-1) ( 2/7ab+xy) ( 2/7ab-xy) (x+y)(m-n)
(x-y)(m+n)
7 x²y-21x²y-14xy=-14x²y-14xy = -14xy(x+1)
-4a²b+6a²b-2ab=2a²b-2ab=2ab(a-1)
就这样哦~前几个应用的平方差公式a²-b²=(a+b)(a-b)直接可得答案的……