# Are x and ix linearly dependant or independant? (i=√-1)

1. Oct 11, 2013

### gikiian

The question is: are x and ix linearly dependent or independent?

My first guess is that they should be linearly dependent since i is a constant.

But when you apply the definition of linear independence i.e. when you solve ax+ibx=0 (where x≠0), you get a=-ib which shows that the only solution can be a,b=0.

Hence, according to definition of linear independence, x and ix should be linearly independent.

Am I correct?

2. Oct 11, 2013

### Simon Bridge

I think you need to be claer about how you are setting up the vector space.
i.e. In the complex plane, ix is perpendicular to x.

Only if you insist that a and b are both real.
The definition applies over a subset of a vector space - which vector space do these two numbers belong to?

3. Oct 11, 2013

### pwsnafu

In what vector space, with what field?

Linear dependence has nothing to do with whether something is a constant.

Why? $b=2$ and $a=-2i$ is also a solution.

Consider the complex numbers as a one dimensional vector space over itself. What happens?