Question

设A=2x²-3xy+y²-x+2y,B=4x²-6xy+2y²-3x-y,若│

Answer 1

因为,│x-2a│+(y+3)²=0

由非负性可得,

x-2a=0且y+3=0

解得,x=2a,y=-3

又,B-2A=-x-5y=a

所以,

2(x+5y)+x=0

即,3x+10y=0

将y＝-3代入,得3x-30=0

解得,x=10

所以,

A=2x²-3xy+y²-x+2y

=200+90+9-10-6

=299-16

=283