Question

已知x分之一减y分之一等于(x-y)分之一,求x分之y+y分之x的值

Answer 1

1/x-1/y=1/(x-y)

(y-x)/xy=1/(x-y)

xy=-(x-y)²

x²+y²-2xy=-xy

x²+y²=xy

则：

x分之y+y分之x

=(x²+y²)/xy

=xy/xy

=1