# Multiple Righthand Sides

In a case in which a system of linear equations has more than one right-hand side vector, it is most economical to find the solution vectors by first factoring the coefficient matrix A into products of triangular matrices. Then, the resulting triangular systems of linear equations are solved for each right-hand side. When A is a real general matrix, compute access to the LU factorization of A by using the IMSL_LUFAC procedure. The solution xk for the k-th right-hand side vector bk is then found by two triangular solves, Lyk = bk and Uxk = yk. The IMSL_LUSOL function is called with the computed factorization and is used to solve each righthand side. You can follow this process when using other functions for solving systems of linear equations