MATLAB线性方程组的两种求解,matlab求解线性方程组

直接解法

Ax=l，求x。利用逆矩阵、矩阵除法、x=inv(A'A)*A'l

lind.m文件如下，

%求解线性方程组

% x1 + 2x2 + 3x3 + 9x4 = 5

%2x1 + 2x2 + 5x3 + 4x4 = 2

%3x1 + 5x2 + x3 + 5x4 = 3

%7x1 + 4x2 + 2x3 -10x4 = 8

A=[1 2 3 9;2 2 5 4;3 5 1 5;7 4 2 -10];

b=[5 2 3 8]';

x=A\b

c=inv(A)*b

d=inv(A'*A)*A'*b

输出

>> lind.m

x =

4.9227

-3.2373

-1.1680

1.1173

c =

4.9227

-3.2373

-1.1680

1.1173

d =

4.9227

-3.2373

-1.1680

1.1173

Warning: Direct access of structure fields returned by a function call (e.g.,

call to lind) is not allowed. See MATLAB 7.10 Release Notes, "Subscripting Into Function Return