x的相反数是3y+1,y的相反数是2x-1所以x=-(3y+1)y=-(2x-1)x=-(3y+1)=-3y-1代入y=-(2x-1)y=-[2(-3y-1)-1]=-2(-3y-1)+1=6y+2+1=6y+35y=-3y=-3/5x=-(3y+1)=4/5所以(x+y)²=(4/5-3/5)²=1/25