Question

若1/x-1/y=2 xy/x方-y方的值为几?

Answer 1

由1/x-1/y=2得(y-x)/xy=2 y-x=2xy

xy/(x²-y²)==xy/[(x+y)(x-y)]=-xy/[(x+y)(y-x)]=-xy/[2xy(x+y)]=-1/[2(x+y)]