x+7=yx+7=yx+7=y
3x2+3y2+2xy−12x+12y+4=03 x^{2}+3 y^{2}+2 x y-12 x+12 y+4=03x2+3y2+2xy−12x+12y+4=0
3x2+2x=73 x^{2}+2 x=73x2+2x=7
3x2−3y2−2xy+12x+4=03 x^{2}-3 y^{2}-2 x y+12 x+4=03x2−3y2−2xy+12x+4=0