25(x+y)²-9(x-y)²
=[5(x+y)-3(x-y)][5(x+y)+3(x-y)]
=(2x+8y)(8x+2y)
=4(x+4y)(4x+y)

（x+y）²-4（x+y-1）.
=（x+y）²-4（x+y)+4
=(x+y-2)^2還有幾題：a²-x²-2x-2a；1-m²-n²+2mn；x的4次方-5x²+4不好意思啊，麻煩你了。。。a²-x²-2x-2a=(a-x)(a+x)-2(x+a)=(a-x-2)(a+x) 1-m²-n²+2mn=1-(m-n)^2=(1-m+n)(1+m-n) x^4-5x^2+4=(x^2-1)(x^2-4)=(x-1)(x+1)(x-2)(x+2) 先采納后求助哦