5.设F1F_{1}F1、F2F_{2}F2是两定点,∣F1F2∣=6\vert F_{1}F_{2}\vert =6∣F1F2∣=6,动点PPP满足∣PF1∣−∣PF2∣=6\vert PF_{1}\vert -\vert PF_{2}\vert =6∣PF1∣−∣PF2∣=6,则动点PPP的轨迹是((( )))