# I have a matrix A of order 3 X 7 and C is a matrix made

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Srikar Kalivarapu on 1 Nov 2016
Answered: Moe_2015 on 1 Nov 2016
I have a matrix A of order 3 X 7 and C is a matrix made of first , fourth and seventh columns of A I Need to find a matrix B of order 7 X 3 such that AB=C
A =
1.0000 3.0000 5.0000 7.0000 9.0000 11.0000 13.0000 15.0000
2.5000 2.0000 1.5000 1.0000 0.5000 0 -0.5000 -1.0000
0.2500 0.5000 1.0000 2.0000 4.0000 8.0000 16.0000 32.0000
C= 1.0000 7.0000 13.0000
2.5000 1.0000 -0.5000
0.2500 2.0000 16.0000

Moe_2015 on 1 Nov 2016
B=A\C
B =
1.0000 0.3445 -0.0766
0 0 0
0 0 0
0 0 0
0 0 0
0.0000 0.7943 0.7679
0 0 0
-0.0000 -0.1388 0.3086
>> A*B
ans =
1.0000 7.0000 13.0000
2.5000 1.0000 -0.5000
0.2500 2.0000 16.0000

Changoleon on 1 Nov 2016
>> a = [ 1 3 5 7 9 11 13 15; 2.5 2 1.5 1 0.5 0 -0.5 .1; 0.25 0.5 1 2 4 8 16 32];
>> c = [ 1 7 13; 2.5 1 -0.5; 0.25 2 16];
>> b = 1./(a') * c;
>> b
b =
3.0000 15.4000 76.8000
2.0833 6.8333 36.0833
2.1167 4.0667 18.2667
2.7679 3.0000 9.3571
5.1736 3.2778 4.4444
Inf Inf -Inf
-4.9075 -1.3365 3.0000
25.0745 10.5292 -3.6333
>>
Srikar Kalivarapu on 1 Nov 2016
A*B doesnt give me C again