Question

已知x,y 满足x的平方加y的平方加4分之5等于2 x加y,求x加y分之xy

Answer 1

x方+y方+5/4=2x+y

(x方-2x+1)+（y方-y+1/4)=0

(x-1)方+（y-1/2)方=0

x=1,y=1/2

xy/(x+y)=1/3