Question

x的平方+y的平方=2x+y-5\4 求 xy除以x+y

Answer 1

x^2+y^2=2x+y-5/4

(x^2-2x+1)+(y^2-y+1/4)=0

(x-1)^2+(y-1/2)^2=0

x=1,y=1/2

所以xy/(x+y)=1*1/2/(1+1/2)=1/2/(3/2)=1/3