=(3x^2+8xy+4y^2-4x-4)+2(x^2+4)
=5x^2+8xy+4y^2-4x+4
=(4x^2+8xy+4y^2)+(x^2-4x+4)
=4(x+y)^2+(x-2)^2
=0
x+y=0，x-2=0
x=2，y=-2
The registration time of the preliminary contest of the national middle school students' Mathematical Olympiad is mainly concentrated i