(x+y)^2/25-(x-y)^2/16
=【1/5(x+y)+1/4(x-y)】【1/5(x+y)-1/4(x-y)】
=(9/20x-1/20y)(9/20y-1/20x)
-9+a^2b^2
=(ab+3)(ab-3)
(a+b)^2-4a^2
=(a+b+2a)(a+b-2a)
=(3a+b)(b-a)
如果本题有什么不明白可以追问,
(x+y)^2/25-(x-y)^2/16
=【1/5(x+y)+1/4(x-y)】【1/5(x+y)-1/4(x-y)】
=(9/20x-1/20y)(9/20y-1/20x)
-9+a^2b^2
=(ab+3)(ab-3)
(a+b)^2-4a^2
=(a+b+2a)(a+b-2a)
=(3a+b)(b-a)
如果本题有什么不明白可以追问,