1. 已知点M(−5,0)M(-\sqrt{5},0)M(−5,0),N(5,0)N(\sqrt{5},0)N(5,0),动点PPP满足条件∣PM∣−∣PN∣=4\vert PM\vert -\vert PN\vert =4∣PM∣−∣PN∣=4.则动点PPP的轨迹方程为((( )))