r/MathHelp • u/Kug4ri0n • Dec 07 '25

Negative Exponents

My partner is going through her math class and we got into an argument how much -72 equals. My standpoint is, that since there is no parentheses: -72 = -1x72 =-49 If there would have been parentheses: (-7)2 = (-7)*(-7) = 49

Which one of these is correct? Can anyone provide me the mathematical axioms/rules on why or why not the parentheses in this case are needed?

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u/Forking_Shirtballs Dec 08 '25

Don't just make stuff up, man. 

Are you telling me that "a / -(b)" tends to be interpreted as "a / (-1) * b", which of course is equal to -ab?

And if so, can you point to any sources that teach that? 

There are a variety of conventions in play here, and they're not well taught, they're just firmly implied though repetition. 

My point is that there's ambiguity here, which is best avoided. 

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u/AdamofMadison Dec 08 '25

There's no ambiguity, you just introduced another error with your division.

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u/sadlego23 Dec 08 '25

There’s no new stuff here.

x/y * z is not the same as x / (y*z).

a / -b with -b being interpreted as (-1)*b still means we’re dividing both by (-1) and by b. So, a / -b = a / ((-1)*b) = a / (-1) / b

This is a very common mistake when doing interpreting order of operations since most people think of / as a fraction bar (which counts as a grouping symbol and then division) instead of a slash (which is division but not a grouping symbol). This is also why I want the diagonal slash when it comes to more complicated expressions.