How to solve non-linear equation that contain matrix in it?

Hi, Im quite new to matlab and I need to solve this non-linear equation so that i can understand better to continue with my thesis. The yj, S, and Cj are all in matrix form, and k is the sampling time. lets say my k must be in range of 3 ≤ k ≤ 16. How should I write the matlab code? Your help is much appreciated!