for a given (x,√x) on the curve, its distance to (5,0) can be calculated by pythagoras as:
D = √((5-x)² + √x²) = √(x²-9x+25)
We have to find the lowest D. To calculate that, we can find the minimum of x²-9x+25 which is at 9/2 (remember the -b/2a formula).
So the distance is minimal at the point (9/2, 3/√2)
