1、设F1坐标F1(-c,0),F2(c,0),PF1⊥PF2,PF1方程斜率k1=4/(3+c),PF2方程斜率k2=4/(3-c),二直线相垂直,k1=-1/k2,4/(3+c)=-(3-c)/4,c=5,
a^2-b^2=c^2=25,P(3,4)在椭圆上,代入方程,9/a^2+16/(25-a^2)=1
a^4-50a^2+225=0,(a^2-45)(a^2-5)=0,a=3√5,a=√5
1、设F1坐标F1(-c,0),F2(c,0),PF1⊥PF2,PF1方程斜率k1=4/(3+c),PF2方程斜率k2=4/(3-c),二直线相垂直,k1=-1/k2,4/(3+c)=-(3-c)/4,c=5,
a^2-b^2=c^2=25,P(3,4)在椭圆上,代入方程,9/a^2+16/(25-a^2)=1
a^4-50a^2+225=0,(a^2-45)(a^2-5)=0,a=3√5,a=√5