Posted by Anonymous on .
If P(x,y),F1(3,0), F2(3,0) a
nd 16x^2+25y^2=400,
then
find
PF1+PF2.

maths 
Reiny,
16x^2+25y^2=400 or
x^2/25 + y^2/16 = 1
you have an ellipse where a=5 and b=4
looks like you want the sum of the the two distances from any point on the ellipse to the two focal points.
By definition that is 2a
= 10