Systems of ODE: Converting complex solution to real

Shaybay92
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Homework Statement



So, I have found a general solution to a system of linear first order ODE's and this is what I got:

X = c1v1e^(-1+2i)t + c2v2e^(-1-2i)t

where v1 = [-1+2i, 5], v2=[-1-2i,5]. The question is, how do I now change this solution into its real equivalent? i.e. I don't want any complex numbers in my solution.

I have a textbook which explains but it still doesn't make sense to me how they manage to go from a complex to real solution. Could someone explain step by step? Thanks.
 
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I think they're saying that X=x+yi, just resolve in real and imaginary parts...
 
I don't think so, because it has to still span the solution space, and merely dropping the imaginary parts will not ensure this.
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
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