Question

已知A=X的平方-XY-Y的平方,B=3XY+X的平方,X,Y满足条件（X-3）的平方+（Y+2）的平方=0,求1/2[

Answer 1

∵(x-3)²+(y+2)²=0

∴x-3=0,y+2=0

∴x=3,y=-2

1/2[2(A-B)-3A]+1/3[3(A+3B)-3A]-1/2A

=1/2(2A-2B-3A)+1/3(3A+9B-3A)-1/2A

=1/2(-A-2B)+(1/3)×9B-1/2A

=-1/2A-B+3B-1/2A

=-A+2B

=-(x²-xy-y²)+2(3xy+x²)

=-x²+xy+y²+6xy+2x²

=x²+7xy+y²

=3²+7×3×(-2)+(-2)²

=9-42+4

=-29