利用平方差公式
9（x+y)²-4（x-y）²
=[3(x+y)]²-[2(x-y)]²
=[3(x+y)+2(x-y)][3(x+y)-2(x-y)]
=(3x3y+2x-2y)(3x+3y-2x+2y)
=(5x+y)(x+5y)
9（x+y)²-4（x-y）²分解因式=（5x+y)(5y+x）,我知道这是答案,但是我希望有详细的
利用平方差公式
9（x+y)²-4（x-y）²
=[3(x+y)]²-[2(x-y)]²
=[3(x+y)+2(x-y)][3(x+y)-2(x-y)]
=(3x3y+2x-2y)(3x+3y-2x+2y)
=(5x+y)(x+5y)