A=2x^2-3xy+y^2+x-3y,B=4x^2-6xy+2y^2+4x-y,若｜x-2a|+(y+3)^2=0,且B-2A=a,求A的值．

∵ |x-2a|+(y+3)²=0
∴ x=2a,y=-3
∵ A = 2x²-3xy+y²-x+2y = 8a²+16a+3
B = 4x²-6xy+2y²+3x-y = 16a²+42a+21
∴ B-2A = 16a²+42a+21-2*(8a²+16a+3)
= 10a+15
= a
∴ a = -5/3
∴ A = 8a²+16a+3 = -13/9B的化简可以详细点吗？抱歉，前面解答有误，正确如下：∵ A = 2x²-3xy+y²+x-3y= 2*(2a)²-3*(2a)*3+3²+2a-3*3= 2*(4a²)-18a+9+2a-9= 8a²-16aB = 4x²-6xy+2y²+4x-y = 4*(2a)²-6*(2a)*3+2*3²+4*(2a)-3 = 4*(4a²)-36a+2*9+8a-3 = 16a²-36a+18+8a-3 = 16a²-36a+18+8a-3 = 16a²-28a+15∴ B-2A = 16a²-28a+15 - 2*(8a²-16a) = 16a²-28a+15-16a²+32a = 4a+15 = a∴ a = -5∴ A = 8a²-16a= 8*(-5)²-16*(-5)= 200+80= 280怪不得我算的和你不对了，这个你确定是正确的？B = 4x²-6xy+2y²+4x-y = 4*(2a)²-6*(2a)*(-3)+2*(-3)²+4*(2a)-(-3) = 4*(4a²)+36a+2*9+8a+3 = 16a²+36a+18+8a+3 = 16a²+42a+21