Question

已知x分之1-y分之1=3，求y+2xy-x分之2y-3xy-2x的值

Answer 1

1/x-1/y=3
(y-x)/(xy)=3
y-x=3xy
(2y-3xy-2x)/(y+2xy-x)
=[2(y-x)-3xy]/[(y-x)+2xy]
=(6xy-3xy)/(3xy+2xy)
=(3xy)/(5xy)
=3/5

Answer 2

1/X-1/Y=(Y-X)/XY=3即Y-X=3XY;
Y+2XY-X=Y-X+2XY=3XY+2XY=5XY;
2Y-3XY-2X=2(Y-X)-3XY=6XY-3XY=3XY;
Y+2XY-X分之2Y-3XY-2X=3XY/5XY=3/5