曲线x^2/25+y^2/9=1与曲线x^2/(25－k)+y^2/(9-k)=1(k
问题描述：
曲线x^2/25+y^2/9=1与曲线x^2/(25－k)+y^2/(9-k)=1(k
答
焦点相同
x^2/25+y^2/9=1
c^2=25-9=16
x^2/(25－k)+y^2/(9-k)=1
C'^2=(25-k)-(9-k)=16
所以选2