Why Does -3^2 Equal -9 Instead of 9?

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  • Thread starter Thread starter RestlessMind
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Discussion Overview

The discussion revolves around the interpretation of the expression -3^2 and why it evaluates to -9 instead of 9. Participants explore the rules of exponentiation and the order of operations, focusing on the implications of negative signs in mathematical expressions.

Discussion Character

  • Conceptual clarification, Debate/contested, Mathematical reasoning

Main Points Raised

  • One participant expresses confusion about why -3^2 results in -9, noting that multiplying two negatives should yield a positive.
  • Another participant clarifies that the expression is interpreted as - (3^2), which leads to -9, while (-3)^2 would equal 9.
  • A third participant suggests that calculators interpret -3^2 as -32, not as (-3)2, and provides a method to enter the expression correctly to achieve the intended result.
  • A later reply acknowledges the clarification provided by the second participant.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the interpretation of the expression, as there are competing views on how the negative sign interacts with the exponentiation.

Contextual Notes

The discussion highlights the importance of parentheses in mathematical expressions and how different interpretations can lead to different results. The assumptions about order of operations and calculator input methods are also relevant.

RestlessMind
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I thought powers were things like (using the example in the title): -3 * -3 = 9

But when I enter -3^2 in my calculator, I get -9. I thought a negative multiplied by a negative was a positive. What's going on here?
 
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It squares the three before multiplying by negative one.

(-3)2 = (-3)(-3) = 9
-32 = -(3)(3) = -9
 


The calculator assumes that you mean -32, not (-3)2. Try entering 3, then using the +/- key to change its sign, then hit the square key.
 


Ah, I see! Thanks very much!
 

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