2y²+8y+7＝0 -1/2x²-3x=12(y²+4y)+7=0 -1/2(x²+6x)=12(y+2)²-1=0 x²+6x=-2(y+2)²=1/2 (x+3)²=-2+9y+2=±√2/2 x+3=±√7y= -2+√2/2,或-2-√2/2 x= -3+√7,或-3-√7...