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September 22nd, 2019, 10:13 AM   #1
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Order of operation

My daughter has a math problem that both me and my wife got incorrect due to order of operations.
The problem is: (2 3/4 - 3.5) * (-2^2)

Solving each term between the brackets = (11/4 - 14/4) * (4) = (-3/4) * (4) = - 12/4 = - 3.

The correct answer and method according to the key is as follows....

(-3/4) * (-2^2) = (3/4) * (2^2) = 3.....
What is this black magic where you are allowed to multiply each term between brackets by - 1 before raising - 2 to the powers of 2? Shouldn't powers go before multiplication?

Help would be appreciated!
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September 22nd, 2019, 10:33 AM   #2
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We had a discussion about this several weeks ago. I think the consensus was that by convention, -2^2 without brackets does not mean (negative two) squared, but the negative of (two squared). The same as $\displaystyle e^{-x^2}$ means $\displaystyle \frac{1}{e^{x^2}}$.

Incidentally, I was in the camp that initially thought the same as you.
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September 22nd, 2019, 10:49 AM   #3
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The fun of it is that if you type it out in python you get 3. If you put it into open office calc you get - 3.

So that could cause a lot of damage 😕

Since renown software gives different answers I'm not sure how mere mortals should treat this...

Thanks for the answer though. It's appreciated
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September 22nd, 2019, 11:08 AM   #4
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Math Focus: Area of Circle
Which means developers of Python are smarter. Although OpenOffice may have been developed in Python, I am not sure.
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September 22nd, 2019, 11:13 AM   #5
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Someone went to the trouble of performing a survey of various coding languages' interpretations, and basically the conclusion was: when in doubt, use brackets.
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September 22nd, 2019, 11:22 AM   #6
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Quote:
Originally Posted by DarnItJimImAnEngineer View Post
Someone went to the trouble of performing a survey of various coding languages' interpretations, and basically the conclusion was: when in doubt, use brackets.
Agreed... However in this case I was never in doubt. So yes... That's a bit scary...
Also I deal with a lot of rules and regulations.. That are written in that form.

How am I to know in what camp the regulator was when writing the rules....

Really scary stuff...
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