Why doesn't √(x²) = ±√9 when solving x² = 9?

Context: High School
Thread starter Dr. Mirrage
Start date Jul 13, 2009
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Hurkyl

Staff Emeritus

Science Advisor

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Jul 18, 2009

Dr. Mirrage said:

So, then the only question I still have is when should I use the plus/minus sign?

When it makes things easier -- when it makes it easier for you to (correctly) solve a problem, when it makes it easier for you to explain something, and so forth.

If you don't find it makes things easier, then don't use it.

Why doesn't √(x²) = ±√9 when solving x² = 9?

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