已知1/x-1/y=3,则{2x-14xy-2y}/{x-2xy-y}的值为多少
问题描述:
已知1/x-1/y=3,则{2x-14xy-2y}/{x-2xy-y}的值为多少
答
已知1/x-1/y=3
则(y-x)/xy=3
即x-y=-3xy
代入
{2x-14xy-2y}/{x-2xy-y}
=2[(x-y)-7xy]/[(x-y)-2xy]
=2[-3xy-7xy]/[-3xy-2xy]
=-2×10xy/[-5xy]
=4