Power of a Discrete time signal I was learning on power of signal and i went through different formula in internet .

I get different results when i go through internet .



But in other site average power is  written as 



I dont know if both are different formula for different condition .

Thanks in advance
The power of a discrete-time signal $x[n]$ is given by

$$P_x=\lim_{N\rightarrow\infty}\frac{1}{2N+1}\sum_{n=-N}^{N}|x[n]|^2$$

which is identical to the first formula in your question. The second formula is wrong and does not even make any sense due to the infinite limits of the sum.

I'd advise you to use text books or high-quality internet resources such as MIT OpenCourseWare.