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  • 1 Post By DarnItJimImAnEngineer
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September 11th, 2019, 07:37 AM   #1
Joined: Sep 2019
From: Sri Lanka

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What is this theory called?

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

I was said that above equation is false.

And also,

$\displaystyle \sqrt{a^2}=\left|a\right|$

$\displaystyle \mathrm{For}\:a\ge \:0\:\mathrm{rewrite\:}\:\sqrt{a^2}=\left|a\right| \:\mathrm{\:as}\:\sqrt{a^2}=a$

$\displaystyle \mathrm{For}\:a<0\:\mathrm{rewrite\:}\:\sqrt{a^2}= \left|a\right|\:\mathrm{\:as}\:\sqrt{a^2}=-a$

What is this theory and where can I found more about this theory?
deSilvaM is offline  
September 12th, 2019, 12:38 PM   #2
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From: USA

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I don't know about a theory, but every mathematical convention I have ever seen took √ to represent the principal square root, which is exactly what you have described (for positive, real numbers).
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