Where is written:
\( \sqrt {4} = 2 \\ \sqrt {4} \neq-2\)
?
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.
Where is written?
Thank you Geno,but is there somewhere to read?
Try: http://mathworld.wolfram.com/PrincipalSquareRoot.html
Thank you Alan!
Everything is clear now.
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