上题就算了 x^2-(y-z)^2分之x^2-y^2除以（x-y）^2-z^2分之x^2+2xy+y^2乘以x^2-xy分之x^2+xy-xz

上题就算了 x^2-(y-z)^2分之x^2-y^2除以（x-y）^2-z^2分之x^2+2xy+y^2乘以x^2-xy分之x^2+xy-xz
上题就算了 x^2-(y-z)^2分之x^2-y^2除以（x-y）^2-z^2分之x^2+2xy+y^2乘以x^2-xy分之x^2+xy-xz

上题就算了 x^2-(y-z)^2分之x^2-y^2除以（x-y）^2-z^2分之x^2+2xy+y^2乘以x^2-xy分之x^2+xy-xz
原式=(x+y)(x-y)/(x+y-z)(x-y+z)÷(x+y)²/(x-y+z)(x-y-z)×x(x+y-z)/x(x-y)
=(x+y)(x-y)/(x+y-z)(x-y+z)×(x-y+z)(x-y-z)/(x+y)²×(x+y-z)/(x-y)
=(x-y)(x-y-z)/(x+y-z)(x+y)×(x+y-z)/(x-y)
=(x-y-z)/(x+y)

什么

y^2)/[x^2-(y-z)^2] ÷ [x^2+2xy+y^2]/[(x-y)^2-z^2] × [x^2+xy-xz]/[x^2-xy]
x^2-=(x-y)(x+y)/(x+y-z)(x-y+z) × (x-y+z)(x-y-z)/(x+y)(x+y) × x(x+y-z)/x(x-y)..............因式分解
=(x-y-z)/(x+y) .....................约去相同项