The letter C in equations, where did it come from?

Question

JavaScript

I calmly solved all the matrices except for those where C is present in the answers, what does it mean?

Answer 1

Insert this line before the if and you will see why prompt returns an empty string, not null

Answer 2

Redefined system. The solution is some kind of linear subspace, of dimension such as the number of different c.
Imagine that you have crossed three planes (solving a system of three equations with three unknowns).
You can get a plane (if all three are the same) - this is a space of dimensions two, two letters.
You can get a straight line (dimension 1), one letter
And you can get a dot - there will be no letters at all.
Kurosh's textbook will help you.