Question

若x分之1减y分之1等于3,求x-2xy-y分之2x+3xy-2y

Answer 1

(1/x)-(1/y)=3

===> (y-x)/(xy)=3

===> y-x=3xy

===> x-y=-3xy

所以,原式=[(x-y)-2xy]/[2(x-y)+3xy]

=(-3xy-2xy)/(-2*3xy+3xy)

=(-5xy)/(-3xy)

=5/3