4. Let $X$ be a random variable and let $g(x)$ be a nonnegative function. For any $r > 0$, then show that $P(g(x) \ge r) \le \frac{E(g(x))}{r}$. (15 points)
4. Let $X$ be a random variable and let $g(x)$ be a nonnegative function. For any $r > 0$, then show that $P(g(x) \ge r) \le \frac{E(g(x))}{r}$. (15 points)