Maybe I should apologize for this silly question, but the documentation for
Indexed is very short and not explicit.
I have an equation with variables
Indexed[x,n] and construct a sparse matrix through
How can I choose all $x$ with an index value $n≥|b|$ as variables in
And how can I set a rule of substitution for an indexed variable? Construction of form
Indexed[x,1]=a^2 doesn't work, so what's the correct variant?
Thank you in advance for your help