已知多项式AB满足A+3分之1B等于0且B=3x²-6xy+3y² 求A的表达式：若x-1的绝对值+（y+2）²=0

A+1/3B=0,B=3x²-6xy+3y² A=-1/3B=-1/3(3x²-6xy+3y²)=-x²+2xy-y² (x-1)的绝对值+（y+2）²=0x-1=0,y+2=0x=1,y=-2A=-x²+2xy-y² = -(x-y)² = -(1+2)² = -9B= 3x...