已知x／y=3,求x²＋2xy-3y²／x²－xy

已知x／y=3,求x²＋2xy-3y²／x²－xy＋y²的值

1个回答

(x²＋2xy-3y²)／(x²－xy＋y²)
=(x/y+2-3y/x)/(x/y-1+y/x) (分子分母同时除以xy)
=[3+2-3*(1/3)]/[3-1+(1/3)]
=4/(7/3)
=12/7