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#1
12-02-2005, 07:56 PM
 maurile Member Join Date: Mar 2003 Posts: 95
Simple math/syntax problem

This caused a 35-page argument on another forum. Let's see how quickly a consensus is arrived at here.

-5² = ???
#2
12-02-2005, 08:35 PM
 purnell Senior Member Join Date: Jul 2004 Posts: 154
Re: Simple math/syntax problem

[img]/images/graemlins/confused.gif[/img]

(-5)^2 = 25

- (5^2) = -25

30 pages? I must have no idea what I'm talking about if there is an argument.
#3
12-02-2005, 08:42 PM
 maurile Member Join Date: Mar 2003 Posts: 95
Re: Simple math/syntax problem

[ QUOTE ]

(-5)^2 = 25

- (5^2) = -25

[/ QUOTE ]
Everybody agrees that (-5)^2 = 25 and -(5^2) = -25.

The question is which of those two possibilities -5^2 represents.

Without any parentheses, what's the correct order of operations? Do you square the five and then make the result negative? Or do you make the five negative and then square it?

It's really a syntax problem rather than a math problem, but some people say it's ambiguous, some people say it's unambiguously 25, and some say it's unambiguously -25.

There does appear to be a correct answer according to what is apparently the standard convention.
#4
12-02-2005, 08:51 PM
 purnell Senior Member Join Date: Jul 2004 Posts: 154
Re: Simple math/syntax problem

[ QUOTE ]
Without any parentheses, what's the correct order of operations?

[/ QUOTE ]

I don't know. There must be a convention, but since I don't know what it is, I have to rely on the parentheses. Is there some organization in charge of this?
#5
12-02-2005, 08:59 PM
 maurile Member Join Date: Mar 2003 Posts: 95
Re: Simple math/syntax problem

[ QUOTE ]
Is there some organization in charge of this?

[/ QUOTE ]
I don't think there's an official organization, but all the highschool math teachers and highschool math textbooks that we've encountered so far have given the same response.

Their response was the opposite, however, of the one given by the huge majority of engineers we've sampled.

So it appears to be ambiguous.

All of the math teachers, however, say that it's not ambiguous, that it clearly has an unambiguous answer according to the accepted convention for the order of operations. They are sure about this, and I'm inclined to believe them over the engineers who said "I'm not sure, but if I had to guess I'd pick this one" (and got the opposite answer from the one the teachers gave).

I don't want to give the correct (as judged by the teachers who say they're sure) answer away yet. Let's see if anybody in here feels strongly one way or the other.

I can argue either side (although I side with the teachers).
#6
12-02-2005, 09:13 PM
 TomCollins Senior Member Join Date: Jul 2003 Location: Austin, TX Posts: 172
Re: Simple math/syntax problem

[ QUOTE ]
This caused a 35-page argument on another forum. Let's see how quickly a consensus is arrived at here.

-5² = ???

[/ QUOTE ]

Technically, I believe it's -25. Power goes before sign/subtractingg.
#7
12-02-2005, 10:15 PM
 jason_t Senior Member Join Date: Nov 2004 Location: Another downswing? Posts: 2,274
Re: Simple math/syntax problem

-5^2 = -5 * 5 = -25.

This is the correct order of operations.
#8
12-02-2005, 10:37 PM
 imported_luckyme Junior Member Join Date: Apr 2005 Posts: 1
Re: Simple math/syntax problem

0 - 5^2 = Y
0 = Y + 5^2
-Y = 5^2
-Y = 25
Y = -25

how badly did I screw up?
#9
12-03-2005, 12:22 AM
 Siegmund Senior Member Join Date: Feb 2005 Posts: 415
Re: Simple math/syntax problem

Doesn't speak well for the other forum that they found something to argue about. -25.

Perhaps the easiest way to convince someone of it to look at more complicated expressions like x^2+x+3 and -x^2+x+3, plug x=5 and x=-5 into these, and see the difference in how they get evaluated.
#10
12-03-2005, 12:53 AM
 AlphaWice Member Join Date: Feb 2005 Posts: 90
Re: Simple math/syntax problem

BEDMAS .. look it up on google.

I wonder : if people cannot sort out simple math disputes on SMP, how will they be able to sort out complicated disputes about God?

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