Question

已知x分之一减y分之一等于3,求x减2xy减y分之5x加3xy减y的值

Answer 1

1/x-1/y=3(y-x)/(xy)=3y-x=3xy再代入后面所求的代数式，得(5x+3xy-y)/(x-2xy-y)=(5x+y-x-y)/(x-2xy-y)=4x/(-5xy)=-4/(5y)如果题目没抄错，就只能到这了。