Question

若x2-xy-12y2=0求xy分之x2+y2

Answer 1

x^2-xy-12y^2=0

(x-4y)(x+3y)=0

x=4y或x=-3y

（x²+y²)/xy=x/y+ y/x=4+1/4=17/4

或

x²+y²)/xy=x/y+ y/x=-3-1/3=-10/3