（9x²+6xy+y²)-(4²x+4x+1)+(y²+2y+1)+1=0(3x+y)²-(2x+1)²+(y+1)²+1=0(3x+y)²+1+(y+1)²=(2x+1)²(2x+1)²=1x=-1(3x+y)²+(y+1)²=0y1=3 y2=-1 我的答...