Find the point on the graph of f(x) = the square root of 2x + 10 that is closest to the point (4,0).
I don't even know where to start with this.
Distance formula: $\displaystyle D=\sqrt{(x-x_0)^2+(y-y_0)^2}$. Use (4,0) for (x_0,y_0), x for x, and f(x) for y. This is a common question and has been answered before.