F’(x) = lim h->0 [f (x + h) - f(x)] / h
Substitute formula i and f(x) into the definition above.
=lim h->0 [(1/vx + 1/vh + x^2h + xh^2) - 1/vx]/h
Simplifying
= lim h->0 (1/vh + x^2h + xh^2)/h
Applying property ii and simplifying h
lim h->0 (1 + x^2 + xh)
When h->0
Lim h->0 = 1 + x^2
f’(x) = 1 + x^2
