Given [a,b] a bounded interval, and f \in L^{p} ([a,b]) 1 < p < \infty, we define:
F(x) = \displaystyle \int_{a}^{x} f(t) dt, x \in [a,b]
Prove that exists K \in R such that for every partition:
a_{0} = x_{0} < x_{1} < ... < x_{n} = b :
\displaystyle \sum_{i=0}^{n-1} \frac{| F(x_{i+1}) -...