Maths Q

[KeepItSimpleStupid]

In the 0-2^2, the answer is -4.

See: **broken link removed**

There is a difference between a negative number and subtraction.

-2^3 is a negative number raised to the 3rd powe.

0-2^2 is 2 raised to the second power subtracted from 0 because 04 is meaningless. "0" concatenated to -2^2 or "4". There is no operator between the elements.

 

[DerStrom8]

In the 0-2^2, the answer is -4.

See: **broken link removed**

There is a difference between a negative number and subtraction.

-2^3 is a negative number raised to the 3rd powe.

0-2^2 is 2 raised to the second power subtracted from 0 because 04 is meaningless. "0" concatenated to -2^2 or "4". There is no operator between the elements.

No, raising the number to a power takes place BEFORE it is negated. Here is a direct quote from math forum:

If you ever see the expression -3^2 evaluated as 9, that's incorrect.
The exponentiation is always done before the negation unless there are
parentheses there to indicate otherwise.

However, there are some contexts in which it _looks_ like texts are
saying that -3^2 = 9, but a closer inspection will either reveal a
subtle interpretation or a misunderstanding. For instance, what is the
difference between the following statements:

"If I take negative three and square it, I get nine."
"If I square negative three, I get nine."
"If I evaluate negative three squared, I get negative nine."
"If I take the opposite of three squared, I get negative nine."

All of the above statements are correct. The reason some of them
end up with 9 as the answer and some end up with -9 is that some of
the statements have groupings implied in their phrasing. The first
two statements translate into algebraic notation as (-3)^2 = 9, the
third statement translates to -3^2 = -9, and the fourth statement
translates to -(3^2) = -9.

I'm hoping that's enough to convince you that -2^2 is NOT EQUAL to 4.

 

[killivolt]

Thank you everyone for the bantering. I'm learning a lot Now if I could understand truth tables..........sheesh!

Thanks, Bryan1

 

[KeepItSimpleStupid]

Excel 2003 gets 9 for -3^2 and Wolfram Alpha gets -9. I'd tend to believe the latter.

 

[duffy]

I'm hoping that's enough to convince you

If quoting a post from an internet forum is enough to convince you, I can get you to believe in Bigfoot.

Unary minus is an intrinsic property of numbers. There is nothing to evaluate separately.

 

[DerStrom8]

If quoting a post from an internet forum is enough to convince you, I can get you to believe in Bigfoot.

Hey, what makes you think Bigfoot doesn't exist???

Seriously, though, the people who answer the "forum" that this quote is from are professional mathematicians. At least I found something to support my position, which is more than I can say for you. I'd like to see you come up with something saying that the unary negative comes first when raising a value to a power. From there, we'll compare contexts and see if we can figure something out.

 

[Jon Wilder]

OK...Order of Operations...PEMDAS (Parenthesis Exponents Multiply Divide Add Subtract) -

40 + 40 x 0 + 1 =

Since there are no parenthesis or exponents to deal with, we deal with the multiplication first -

40 x 0 = 0

which nulls out two numbers and leaves us with 40 + 1, which equals 41.

Now...if the equation were -

(40 + 40) x (0 + 1)

The answer would be 80 -

40 + 40 = 80
0 + 1 = 1
80 x 1 = 80

If the equation were -

(40 + 40) x 0 + 1 =

We would get -

40 + 40 = 80
80 x 0 = 0
0 + 1 = 1



Make sense?

 

[DerStrom8]

OK...PEMDAS -

40 + 40 x 0 + 1 =

Since there are no parenthesis or exponents to deal with, we deal with the multiplication first -

40 x 0 = 0

which nulls out two numbers and leaves us with 40 + 1, which equals 41.

Now...if the equation were -

(40 + 40) x (0 + 1)

The answer would be 80 -

40 + 40 = 80
0 + 1 = 1
80 x 1 = 80

If the equation were -

(40 + 40) x 0 + 1 =

We would get -

40 + 40 = 80
80 x 0 = 0
0 + 1 = 1



Make sense?

Thank you, Jon. That is exactly how I see it

 

[DerStrom8]

Okay, I just had to post this here, just to lighten the mood a bit. Thanks to micr0man for the link

https://www.youtube.com/watch?v=SXx2VVSWDMo

 

[duffy]

At least I found something to support my position, which is more than I can say for you. I'd like to see you come up with something saying that the unary negative comes first when raising a value to a power.

Challenge accepted.
https://en.wikipedia.org/wiki/Unary_operator

"As unary operations have only one operand they are evaluated before other operations containing them."

 

[DerStrom8]

Challenge accepted.
https://en.wikipedia.org/wiki/Unary_operator

"As unary operations have only one operand they are evaluated before other operations containing them."

Okay, first thing I noticed on the page was this:

**broken link removed**

Then, after reading through the page, I still don't see anything about raising it to a power. I agree that negative 2 squared is 4. However, if you write it like -2^2, you do not specify that it is -2 you are squaring. Therefore, the order of operations takes precedence.

For future reference, wikipedia is not a good site to use to prove something (especially when it doesn't have citations!!!). Find a quote from a professional mathematician that says the negation must come first and I will stand down.

 

[KeepItSimpleStupid]

Here are the variences explained:

http://zonalandeducation.com/mmts/expressions/raiseToAPower.html

I seem to remember finding this "bug" in Excel many years ago and argued it the right way. This time I checked in Excel, hoping they would have gotten it right, but it from Microsoft and that should have raised a flag. I ended up chasing my tail for checking first using the wrong reference.

BIG OOPS.

PS: I did tell you that I use parenthesis: such as (-1)^3

Time for some cookies?

 

[DerStrom8]

Here are the variences explained:

http://zonalandeducation.com/mmts/expressions/raiseToAPower.html

I seem to remember finding this "bug" in Excel many years ago and argued it the right way. This time I checked in Excel, hoping they would have gotten it right, but it from Microsoft and that should have raised a flag. I ended up chasing my tail for checking first using the wrong reference.

BIG OOPS.

PS: I did tell you that I use parenthesis: such as (-1)^3

Time for some cookies?

Thank you very much for that, KISS. And I'm just going to post a quote from it, so that it's easier to find:

Here is a harder one to understand:

-4^2

Now, the negative sign out front must wait till the raise to a power operation is finished. So, four raised to the second power is sixteen, since four times four is sixteen. After that evaluation the negative sign accepts the value of sixteen as an operand and produces a value of negative sixteen. Therefore, we can write:

-16 = -4^2

 

[duffy]

Find a quote from a professional mathematician that says the negation must come first and I will stand down.

That Wikipedia page references Matt Insall, who is an Associate Professor of Mathematics at Missouri University of Science and Technology.

 

[DerStrom8]

That Wikipedia page references Matt Insall, who is an Associate Professor of Mathematics at Missouri University of Science and Technology.

Referencing is different from quoting, though. If you can find proof that he actually said that, then I will chalk this up to a poorly-written problem.

EDIT: I just looked up the reference, and the page that the link goes to says nothing about a unary operator coming before an exponent.

 

[duffy]

What, you think I'm going to call Matt on the phone?

*ring* *ring* "Hello?"

"Hi, Matt, we were just having an argument on the internet, and I was wondering..."

Anyway, I would say my reference is still better than yours. You got a guy calling himself "Doctor Math" on an internet forum. From this page: https://mathforum.org/dr.math/abt.drmath.html it says: "By the year 2000, there had been over 300 volunteer 'Doctors' from all corners of the globe". Notice 'doctors' is in quotes. In other words, this is just a bunch of blowhards in a forum. Like us.

 

[KeepItSimpleStupid]

I give up: **broken link removed**

This one gives a specific rank to the operators and Unary - and + come first.

Time to find a "real book"

 

[DerStrom8]

What, you think I'm going to call Matt on the phone?

*ring* *ring* "Hello?"

"Hi, Matt, we were just having an argument on the internet, and I was wondering..."

Anyway, I would say my reference is still better than yours. You got a guy calling himself "Doctor Math" on an internet forum. From this page: http://mathforum.org/dr.math/abt.drmath.html it says: "By the year 2000, there had been over 300 volunteer 'Doctors' from all corners of the globe". Notice 'doctors' is in quotes. In other words, this is just a bunch of blowhards in a forum. Like us.

No, Wikipedia is never a good source of proof, ESPECIALLY when there are no citations! It definitely isn't better than the forum, though I can see what you mean when you say the forum isn't much better either.

I give up: **broken link removed**

This one gives a specific rank to the operators and Unary - and + come first.

Time to find a "real book"

Than you, KISS. This is exactly the kind of link I was waiting for duffy to bring up. It clearly states here that the negation has to happen first. So, either the site is downright wrong (which is just as likely as if the sites I posted were wrong) or it is another way to look at it. With that evidence, I can definitely say that the problem is poorly written, though I would still be interested in looking in a textbook. I suppose it all depends on how you were taught. IMO nobody should ever write a problem like this anyway. If you're squaring negative 2, you should just write it as (-2)^2, and if you're negating two squared, you should write -(2^2). Can we at least agree on that part?

 

[KeepItSimpleStupid]

Here is the same argument were're having:

https://www.excelbanter.com/showthread.php?t=95534

With almost the same result. The order is as defined. Their feeling is that -1^3 is "ambiguous" and should be treated as such. Use parenthesis.

No wonder why the Russian's can't launch a rocket?

So, -1^3 has at least two answers that are correct.

If you said -1^3 in C, Matematica, Java, Excel, VB evaluates to (insert -1 or 1 here), only then can you have the correct answer.

I'm tired.

 

[DerStrom8]

Here is the same argument were're having:

https://www.excelbanter.com/showthread.php?t=95534

With almost the same result. The order is as defined. Their feeling is that -1^3 is "ambiguous" and should be treated as such. Use parenthesis.

No wonder why the Russian's can't launch a rocket?

So, -1^3 has at least two answers that are correct.

If you said -1^3 in C, Matematica, Java, Excel, VB evaluates to (insert -1 or 1 here), only then can you have the correct answer.

I'm tired.

-1^3 has only one answer, regardless of how you look at it. (-1)^3=-1, and -(1^3)=-1.

BTW congrats on your 2000th post