Why is a equal to negative a in this scenario?

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Discussion Overview

The discussion revolves around the mathematical reasoning behind the equation \( a = -a \) in a specific scenario involving square roots and complex numbers. Participants explore the implications of manipulating square roots and the conditions under which certain mathematical properties hold.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant proposes that if \( a = b - c \), then manipulating the square root leads to \( \sqrt{a} = -\sqrt{a} \) under certain conditions.
  • Another participant challenges the manipulation of square roots, noting that the property \( \sqrt{ab} = \sqrt{a}\sqrt{b} \) has restrictions, specifically that both \( a \) and \( b \) must be nonnegative.
  • A later reply acknowledges the restriction on square root properties and expresses understanding of the issue raised.
  • Another participant introduces the concept of choosing between \( +i \) and \( -i \) when dealing with \( \sqrt{-1} \), suggesting that the sign choice affects the interpretation of the result.

Areas of Agreement / Disagreement

Participants express differing views on the validity of the mathematical manipulations involving square roots. While some acknowledge the restrictions on square root properties, there is no consensus on the implications of the results derived from these manipulations.

Contextual Notes

The discussion highlights limitations regarding the assumptions made about the values of \( a \), \( b \), and \( c \), particularly in relation to the nonnegativity required for certain square root properties to hold. The implications of choosing between \( +i \) and \( -i \) in complex numbers are also noted but remain unresolved.

noahsdev
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I've been messing around with numbers (as you do) and I'm wondering why this occurs..
lets let a = b-c.
√a
= √(b-c)
=√(-(c-b))
=i√(c-b)
=i√(-(b-c))
=i2√(b-c)
=-√(b-c)
=-√a
For example if you let a = 1, b = 2, and c = 1.
 
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noahsdev said:
I've been messing around with numbers (as you do) and I'm wondering why this occurs..
lets let a = b-c.
√a
= √(b-c)
=√(-(c-b))
=i√(c-b)
The step above is where the problem is. You're using the property that ##\sqrt{ab} = \sqrt{a}\sqrt{b}##
There are restrictions on this and some of the other square root properties - both a and b have to be nonnegative.
noahsdev said:
=i√(-(b-c))
=i2√(b-c)
=-√(b-c)
=-√a
For example if you let a = 1, b = 2, and c = 1.
 
Last edited:
Mark44 said:
The step above is where the problem is. You're using the property that ##\sqrt{ab} = \sqrt{a}\sqrt{b}##
There are restrictions on this and some of the other square root properties - both a and b have to be nonnegative.
That makes sense. Thanks.
 
\sqrt[2]{-1} = \pm i. The choice of the '+' or '-' depends on the situation. So your result is 'a = \pm a' where you must decide which sign is correct.
 

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