+0  
 
+2
390
5
avatar+41 

x2 = -1

 

x = ?

lolomine09  May 17, 2017
 #1
avatar+93654 
+2

There is no real answer, YOu cannot find the squareroot of a negative number but if you know about complex numbers there is an imaginary answer.

 

\(x^2=-1\\x=\pm i\)

Melody  May 17, 2017
 #2
avatar+41 
+3

for what does the kind of mix between '+' and '=' stands for?

lolomine09  May 17, 2017
 #3
avatar+227 
+1

The +- symbol means that the number can be both positive and negative. So, to elaborate on Meoldy's answer, x = -i and  x = +i. You use it whenever you take the square root of a number, as both (-x)^2 and (x)^2 give the same result, without exception.
You'll see this in the quadratic formula: \(x = {-b \pm \sqrt{b^2-4ac} \over 2a}\)

That just means there are two answers, one where the +- sign is positive and one where it's negative.

ThisGuy  May 17, 2017
 #4
avatar+93654 
+1

Thanks ThisGuy.  :)

 

It really means  x=i    OR    x = -i

 

x obviously cannot equal both at once and that is what 'and' means :)

It is a technical difference but it is an important one for both of you to understand :)

Melody  May 17, 2017
 #5
avatar+227 
+1

Ah, my words failed me! Thanks for pointing that out :p

ThisGuy  May 17, 2017
edited by ThisGuy  May 17, 2017

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