# linear equation with summation

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Ben Andersson on 6 Jul 2020 at 9:42
Commented: Ben Andersson on 6 Jul 2020 at 13:41
The equation is given as . D and A are given through matrices. I need to calculate q.
I use operator / to solve linear equation, so that q=A/D. The question is, how to account for summation in this case? q=0,before cycle and then q=q+q;?

madhan ravi on 6 Jul 2020 at 9:43
Paste what you have tried so far?
Ben Andersson on 6 Jul 2020 at 10:06
n=10;
a=0.1:0.1:1;
A=[a;a;a;a;a;a;a;a;a;a;];
d=0.5:0.5:5;
D=[d;d;d;d;d;d;d;d;d;d;];
q=zeros(n,n);
for m=1:n
for t=1:n
for j=1:n
q(m,j)=A(m,t)/D(j,t);
q(m,j)=q(m,j)+q(m,j);
end
end
end

Matt J on 6 Jul 2020 at 13:37
Edited: Matt J on 6 Jul 2020 at 13:37
q=A/D should already account for the summation. Your equation can be written just by replacing the summation with simple matrix multiplication. In this form, the equation is just q*D=A and you have rightly used q=A/D to solve it.

#### 1 Comment

Ben Andersson on 6 Jul 2020 at 13:41
thanks!