已知1/x-1/x=3,求x-xy-y分之5x+xy-5y的值
问题描述:
已知1/x-1/x=3,求x-xy-y分之5x+xy-5y的值
如题
答
设1/x-1/y=t
(5x+xy-5y)/(x-xy-y) = (1-5(1/x-1/y))/(-1-(1/x-1/y))=(5t-1)/(t+1)
至于是1/x-1/y=3还是1/y-1/x=3都差不多