Y轴焦点(0,B)X轴焦点(-B/3,0)B^2=36B=6或B=-6Y=3X+6Y=3X-6
when x=0,y=b;when y=0,x=-b/3S=|b|*|-b/3|/2=6,b^2=36,b=+ -6y=3x+6 或y=3x-6