True or false: If $\mathbf{x}_1^{\star}$ solves $A \mathbf{x}=\mathbf{c}$, and $\mathbf{x}_2^{\star}$ solves $B \mathbf{x}=\mathbf{d}$, then $\mathbf{x}^{\star}=\mathbf{x}_1^{\star}+\mathbf{x}_2^{\star}$ solves $(A+B) \mathbf{x}=\mathbf{c}+\mathbf{d}$.
2.5.20. Under what conditions on the coefficient matrix $A$ will the systems in (2.34) all have a solution?