【参数法】由题意可设点P(3cost,2sint).又焦点F1(-√5,0),F2(√5,0).∴向量PF1·向量PF2=(3cost+√5,2sint)·(3cost-√5,2sint)=9cos²t-5+4sin²t=5cos²t-1＜0.===>cos²t＜1/5.===>(3cost)²＜9/5.===>-3√5/5＜3cost＜3√5/5.即点P横坐标的取值范围是(-3√5/5,3√5/5).