线性方程组的直接解法命令（直接调用）列主元素法对应的 LU分解：L,U = lu(A)L,U,P = lu(A)Cholesky分解：L = chol(A,lower)计算向量或矩阵的范数：n = norm(A,p)；p=1 2 inf计算矩阵的条件数c = cond(X,p) p=1 2 inf计算矩阵的行列式：d = det(A)计算矩阵的逆B = inv(A)计算矩阵的特征值与特征向量：d = eig(A)V,D = eig(A)计算线性方程组的解：x = inv(A)*bx = A b