Find the intersection of parabola 2y = x2 and line y = mx + 2. (U may find only the x coordinate).
U will get x = m + (m2 + 4)1/2
Since x2 > x1,
So, x2 = m + (m2 + 4)1/2
and x1 = m - (m2 + 4)1/2
I = (mx2/2) + 2x + (x3/6) limit of x from x1 to x2
Put the limits and then find dI/dm and put it equal to 0 to get a value of m.
Check thru double derivative that d2I/dm2 > 0.
So, value of m corresponds to minimum value of I.