x^2/9-y^2/16=1.
a^2=9,b^2=16,c^2=9+16=25,c=5
即右焦点的坐标是(5,0)
P(6,m)代入得:36/9-m^2/16=1
得:m^2=48
所以,P到右焦点的距离=根号[(6-5)^2+(m-0)^2]=根号(1+m^2)=根号(1+48)=7