Let Q = (0,4) and R= (9,7) be given points in the plane. We want to find the point P=(x,0) on the x-axis such that the sum of distances PQ+PR is as small as possible.

f(x) = ?

[a,b] a = ? b = ?

The minimal sum of distances is ?

Can anyone show me how to work this, as I am utterly lost. All I can muster is maybe $\displaystyle sqrt(-x^2 + 16) + sqrt((9-x)^2+49)$. I'm all fuggled.