A soma das raízes da equação $\left[\begin{array}{cc}\cos x& 1\\ 3& -1\end{array}\right]\left[\begin{array}{cc}2& 0\\ 1& 1\end{array}\right]=\left[\begin{array}{cc}0& 1\\ 5& -1\end{array}\right]$, onde $0<x<2\pi$, é: