JEE Main 2022 · 29 Jun · Shift 2, Mathematics question 29

Let $M=\begin{bmatrix}0&-\alpha\\\alpha&0\end{bmatrix}$, where $\alpha$ is a non-zero real number an $N=\displaystyle\sum_{k=1}^{49}M^{2k}$. If $\left(I-M^2\right)N=-2I$, then the positive integral value of $\alpha$ is ______.