左边=x^2+4XY+ 4Y^2+10X+aY+b+20y-20y+25-25
=x^2+4XY+ 4Y^2+10X+20y+25-25+aY+b-20y
=(x+2y+5)^2+(a-20)y+
则 a-20=0 b-25>0
则a=20,b>25
左边=x^2+4XY+ 4Y^2+10X+aY+b+20y-20y+25-25
=x^2+4XY+ 4Y^2+10X+20y+25-25+aY+b-20y
=(x+2y+5)^2+(a-20)y+
则 a-20=0 b-25>0
则a=20,b>25