Question

已知x分之1-y分之1=3则x-2xy-y分之2x-5xy-2y的值为几 急a

Answer 1

1/x-1/y=(y-x)/xy=3
y-x=3xy
所以x-y=-3xy
所以原式=[(x-y)-2xy]分之[2(x-y)-5xy]
=[(-3xy)-2xy]分之[2(-3xy)-5xy]
=(-5xy)分之(-11xy)
=5分之11