Question

x分之一－y分之一＝3,求代数式x－2xy－y分之2x－14xy－2y的值

Answer 1

1/x-1/y=3
1/y-1/x=-3
(2x-14xy-2y)/(x-2xy-y)
= 2(x-7xy-y)/(x-2xy-y)
分子分母同除以xy：
= 2(1/y-7-1/x)/(1/y-2-1/x)
= 2(1/y-1/x-7)/(1/y-1/x-2)
= 2(-3-7)/(-3-2)
= 4