[x²-(y-z)²]/[(x+y)²-z²]
=(x-y+z)(x+y-z)(/(x+y+z)(x+y-z)
=(x-y+z)/(x+y-z)
=(x+y-z)(x-y+z)/(x+y+z)(x+y-z)=(x-y+z)/(x+y+z)
分子分解为(x+y-z)(x-y+z)
分母分解为(x+y+z)(x+y-z)
结果分子分母均约掉相同因式得
(x-y+z)/(x+y+z)
解: (x+y-z)(x-y+z) x-y+z
原式= __________ =________________
(x+y+z)(x+y-z) x+y+z
上面是一个平方差公式,下面也是一个平方差公式。