Linear Algebra help...

Orsorum

Lifer
Dec 26, 2001
27,631
5
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This should be a fairly simple problem... but for some reason, I'm not understanding it.

Let x_ijkl (for i,j,k,l equal to 1,2) be the unknowns (variables). We have 16 total variables. Let 'a' be a number which will be determined later. Consider the following system of linear equations:

x_1jk1 = ax_11jk for j = 1,2, k = 1,2
x_1jk2 = ax_21jk + x_11jk for j = 1,2, k = 1,2
x_2jk1 = ax_12jk for j=1,2, k = 1,2
x_2jk2 = ax_22jk + x_12jk

a) rewrite the system of equations in matrix form

I guess I'm just confused as to how the subscripts work in this one... I'm assuming that i and j determine the spot in the matrix... so, then, what to k and l represent?
 

Calin

Diamond Member
Apr 9, 2001
3,112
0
0
It's simple, you have 16 independent variables, named x1111, x1112, etc
You write all the equations and you will have a 16x16 matrix (with lots of coefficients equals to 0)
So it's bidimensional.
Or if you want, you may "rename" variables x1111=Xa, x1112=Xb, x1113=Xc etc.