_S_o_l_v_e _a_n _U_p_p_e_r _T_r_i_a_n_g_u_l_a_r _S_y_s_t_e_m
	
	     backsolve(r, x, k=ncol(r))
	
	_A_r_g_u_m_e_n_t_s:
	
	           r : an upper triangular matrix giving the coeffi-
	               cients for the system to be solved.  Values
	               below the diagonal are ignored.
	
	           x : a matrix whose columns give ``right-hand
	               sides'' for the equations.
	
	           k : The number or columns of r and rows of x to
	               use.
	
	_V_a_l_u_e:
	
	     The solution of the triangular system.  The result will
	     be a a vector if x is a vector and a matrix if x is a
	     matrix.
	
	_R_e_f_e_r_e_n_c_e_s:
	
	     Dongarra, J. J., J. R. Bunch, C. B. Moler and G. W.
	     Stewart (1978).  LINPACK Users Guide.  Philadelphia:
	     SIAM Publications.
	
	_S_e_e _A_l_s_o:
	
	     chol, qr, solve.
	
	_E_x_a_m_p_l_e_s:
	
	     # no examples yet