a=2b即a^2=4b^2(1)当椭圆焦点在x轴时,设椭圆方程为x^2/(4b^2)+y^2/b^2=1将点P代入,得：9/(4b^2)=1∴b^2=9/4∴椭圆方程为x^2/9+y^2/（9/4）=1（2）当焦点在y轴时,设椭圆方程为x^2/b^2+y^2/(4b^2)=1将点P代入,得：9/b^...