+0

# agreement?

+2
205
4
+7189

Where is written:

$$\sqrt {4} = 2 \\ \sqrt {4} \neq-2$$

?

asinus  Sep 29, 2017
Sort:

#1
+17711
+3

There are two square roots of 4:  2  and  -2.

The positive square root is called the "principal root".

The square root sign is defined to mean the principal root; thus, sqrt(4) = 2, not -2.

geno3141  Sep 30, 2017
#2
+7189
0

Where is written?

Thank you Geno,
but is there somewhere to read?

?

asinus  Sep 30, 2017
#3
+26402
+1

Try:  http://mathworld.wolfram.com/PrincipalSquareRoot.html

Alan  Sep 30, 2017
#4
+7189
+1

Thank you Alan!

Everything is clear now.

!

asinus  Sep 30, 2017

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