+0

# x 2 = -1

+2
390
5
+41

x2 = -1

x = ?

lolomine09  May 17, 2017
#1
+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
+41
+3

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

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

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

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