Question

设A=2x方-3xy+y方-x+2y,B=4x方-6xy+2y方+3x-y.若|x-2a|+（y+3）的平方=0,且B-

Answer 1

∵|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=-13/9