矩阵和行列式的一种应用是,它可以用于求解两个或三个变量中的线性方程。矩阵和行列式还用于检查任何系统的一致性,无论它们是否一致。
使用矩阵逆解线性方程组
线性方程组的解可以使用矩阵的逆来求出。让等式为:
a 1 x + b 1 y + c 1 z = d 1
a 2 x r + b 2 y + c 2 z = d 2
a 3 x + b 3 y + c 3 z = d 3
这些方程可以使用矩阵表示如下
此外,这可以写成
此外,该系统可以写成
轴= B
其中矩阵A包含未知变量的系数。
A =
矩阵X是包含未知变量的列矩阵。
X =
矩阵B也是一个列矩阵,它包含常量。
B =
因此,如上所述,线性方程组可以转换为矩阵形式,可以写成:
轴= B
如果A是非奇异矩阵,则存在A -1。
两边都乘以A -1
A -1轴= A -1 B
IX = A -1 B
X = A -1 B
这为未知变量提供了唯一的解决方案。该解决方案将是唯一的,因为任何非奇异矩阵都具有唯一的逆。
如果A是一个奇异矩阵,则A -1不存在。在这种情况下| A | = 0,因此您将不得不计算(adj A)B。
1.如果(adj A)B≠O,则线性方程组不存在任何东西,并且该系统将不一致。
2.如果(adj A)B = O,则线性方程组将具有零解或无穷多个解,这就是为什么该系统在没有任何解的情况下可能会不一致,或者在无穷多个时可能会保持一致的原因解决方案。
系统一致性
根据方程组拥有的解决方案数量,称其为一致或不一致。
- 一致的系统:如果方程组具有解,则称其为一致的。
- 不一致的系统:如果方程组不具有解决方案,则称其为不一致的。
样本问题
问题1.使用矩阵求解以下线性方程
2x + y = 3
2x + 3y = 6
解决方案:
The above system of linear equations can be written in the form of AX = B where A is the matrix of coefficients, X is the matrix of unknown variables and B is the matrix of constants.
A =
X =
B =
First find out the |A|
as you can see |A| = 4 ≠ 0. Hence, the system of equations is consistent and will possess an unique solution and the solution can be found out using X = A-1B
A-1 =
X = A-1B
=
=
=
From here, you can conclude that
x = 3/4
and y = 6/4
问题2。说给定系统是否一致
x + 3y = 5
2x + 6y = 8
解决方案:
The above system of equations can be written in the form of AX = B, where
A =
X =
B =
Now check determinant of A
|A| = 6 – 6 = 0g
For checking consistency of the system, you have to check (adj A)B
adj A =
(adj A)B =
(adj A)B =
(adj A)B =
Since (adj A)B ≠ 0, the solution of the given system of linear equations doesn’t exist. Hence, the system of equations is inconsistent.
问题3:使用矩阵法求解线性方程组
x – y + 2z = 7
3x + 4y – 5z = -5
2x – y + 3z = 12
解决方案:
The above system of equations can be written in the form of AX = B, where
A =
X =
B =
Now check determinant of A
|A| = 1 * (12 – 5) + 1 * (9 + 10) + 2 * (-3 – 8)
|A| = 7 + 19 – 22 = 4
|A| ≠ 0
Hence, its inverse exists and hence there exists a unique solution that can be found out by X = A-1B
A-1 =
X = A-1B
=
=
=
=
From here, you can see that x =2, y = 1, and z = 3.
Hence, x = 2, y = 1, and z = 3.