由|x-2a|+(y+3)²=0得：x=2a,y=-3,
B-A=(4x²-6xy+2y²+3x-y)-2(2x²-3xy+y²-x+2y)
=5X-5Y
∴10a+15=a
9a=-15
a=-5/3.那A咧？？我求大A不是小a........X=-10/3，y=-3A=2x²-3xy+y²-x+2y=2(-10/3)^2-3(-10/3)*(-3)+(-3)^2-(-10/3)+2(-3)=200/9-30+9+10/3-6=230/9-27=-13/9