(1/x+1/y+1/z)×(xy)/(xy+yz+zx)

问题描述:

(1/x+1/y+1/z)×(xy)/(xy+yz+zx)

通分
原式=[(yz+xz+xy)/xyz]×(xy)/(xy+yz+zx)
=xy(yz+xz+xy)/[xyz(xy+yz+zx)]
=1/z