已知xy满足x²+y²+5/4(四分之五)=2x+y,求代数式(x+y)xy
x²+y²+5/4=2x+y
x²-2x+1+y²-y+1/4=0
(x-1)²+(y-1/2)²=0
∴x-1=0 y-1/2=0
x=1 y=1/2
∴(x+y)xy=(1+1/2)*1*1/2=3/2*1/2=3/4