VD19: Giải hệ : 10x
1
+ 2x
2
+ 3x
3
+ 4x
4
= 5
2x
1
+ 10x
2
+ 6x
3
+ 7x
4
= -1
3x
1
+ 6x
2
+ 20x
3
+ 5x
4
= 4.3
4x
1
+ 7x
2

+ 7x
3
= 5
-x
1
+ 4x
2
+ 4x
3
= 2
x
1
+ 10x
2
+ 18x
3
= 12
>> A=[1 3 7;-1 4 4;1 10 18]
A =
1 3 7
-1 4 4
1 10 18
>> B=[5;2;12]
B =
5
2
12
>> det(A)
ans =
0

4
+

7x
5
= 2
-x
1
+ 2x
2
+ 2x
3
+ 2x
4
+ x
5
= 0
-2x
1
+ 5x
2
- 4x
3
+ 9x
4
+

7x
5
= -0.5

4 5 6
7 8 9
10 11 12
>> B=[1;3;5;7]
B =
1
3
5
7
>> rank(A)
ans =
2
>> rank([A B])
ans =
2
>> X=pinv(A)*B
X =
0.3889
0.2222
0.0556