Question: How do I get an exact number out of this function?

Wus poppin Jimbos

My function is as follows:

f(x)=(10000/1+30762*0.478^x)+5

I can then type 

maximize(f'(x))

And I get the result which is approximately 1845.361367

I then assign at a name e.g. "M"

I then try and execute the command (where I isolate the expression for x)

f'(x)=M

I get the result

 
              x = 14.00001597 - 0.00005369289477 I

Which is super annoying to look at..

Is there any way that I can remove the - 0.00005369289477 I part? And just get the answer (which should be 14)

I have no problem executing 

diff(f(x), x) = 1845.361366;
 = 
                             "(->)"

                        x = 13.99997555

However 1845.361367 once again gives me x = 14.00001597 - 0.00005369289477 I

Any help is appreciated <3