\[ E_x = \sum_{n=-\infty}^{+\infty} \left| x\left[ n \right] \right|^2 \]
\[ P_x = \lim_{N\to\infty} \frac{1}{2N + 1} \sum_{n = -N}^{N} \left| x[n] \right|^2\]
\[ E_x = \sum_{n=-\infty}^{+\infty} \left| x\left[ n \right] \right|^2 \]
\[ P_x = \lim_{N\to\infty} \frac{1}{2N + 1} \sum_{n = -N}^{N} \left| x[n] \right|^2\]