Author Topic: -5² = -25  (Read 1265 times)

Simon_Seagull

  • Posts: 53
Re: -5² = -25
« Reply #20 on: July 30, 2009, 05:07:04 pm »
Quote from: "Fubsadoo"
Quote from: "Krask"
Quote from: "SamGibz"
ok thats in correct. whats a +ive multiplied by a +ive. Its a +ive. Whats a -ive multiplied by a +ive. It is a -ive. Whats a -ive multiplied by a -ive. A +ive. -5^2 i s basically saying -5 * -5. We know 2 minuses make a plus hence -5^2 = 25. Therefore-5^3 = -125. minus*minus*minus = positve * negative. So Negative. However, the square root ok 25 is either -5 or +5. Pure Maths, love it!

That's not the question though. -5² is -(5x5) because the power is the first thing to be calculated (PEMDAS)

Na ah, BIDMAS.
BIDMAS= Brackets Indices Division/Multiplication Adding/Subtracting

Indices = Powers

Shask

  • Posts: 254
Re: -5² = -25
« Reply #21 on: July 30, 2009, 05:14:52 pm »
Quote from: "Fubsadoo"
Quote from: "Krask"
Quote from: "SamGibz"
ok thats in correct. whats a +ive multiplied by a +ive. Its a +ive. Whats a -ive multiplied by a +ive. It is a -ive. Whats a -ive multiplied by a -ive. A +ive. -5^2 i s basically saying -5 * -5. We know 2 minuses make a plus hence -5^2 = 25. Therefore-5^3 = -125. minus*minus*minus = positve * negative. So Negative. However, the square root ok 25 is either -5 or +5. Pure Maths, love it!

That's not the question though. -5² is -(5x5) because the power is the first thing to be calculated (PEMDAS)

Na ah, BIDMAS.

No. They're the same.

B = Brackets, P = Parantheses (same thing)
I = Indices, E = Exponentials
DM/MD same
AS same

 :D
eRepublik Username: Shask

ajholman

  • Posts: 253
Re: -5² = -25
« Reply #22 on: July 30, 2009, 05:24:42 pm »
Quote from: "Krask"
That's not the question though. -5² is -(5x5) because the power is the first thing to be calculated (PEMDAS)

The minus sign there isn't an operator, it is signifying that the number is negative. So it is -5 x -5 = 25.
Try putting =-5^2 in Excel and seeing what it gives you.

Simon_Seagull

  • Posts: 53
Re: -5² = -25
« Reply #23 on: July 30, 2009, 05:27:14 pm »
Quote from: "ajholman"
Quote from: "Krask"
That's not the question though. -5² is -(5x5) because the power is the first thing to be calculated (PEMDAS)

The minus sign there isn't an operator, it is signifying that the number is negative. So it is -5 x -5 = 25.
Try putting =-5^2 in Excel and seeing what it gives you.
What does excel know? It's made by Americans.

Shask

  • Posts: 254
Re: -5² = -25
« Reply #24 on: July 30, 2009, 05:33:14 pm »
Quote from: "ajholman"
Quote from: "Krask"
That's not the question though. -5² is -(5x5) because the power is the first thing to be calculated (PEMDAS)

The minus sign there isn't an operator, it is signifying that the number is negative. So it is -5 x -5 = 25.
Try putting =-5^2 in Excel and seeing what it gives you.

Incorrect. By putting -5² you are signifying that the minus sign is the operator. Whereas if you put (-5)², you would be swapping it so that the minus sign is to create a negative 5.
eRepublik Username: Shask

Fubsadoo

  • Posts: 336
Re: -5² = -25
« Reply #25 on: July 30, 2009, 05:45:00 pm »
Quote from: "Krask"
Quote from: "Fubsadoo"
Quote from: "Krask"

Na ah, BIDMAS.

No. They're the same.

B = Brackets, P = Parantheses (same thing)
I = Indices, E = Exponentials
DM/MD same
AS same

 :D

Yeah I know, it's just PEMDAS is a bit more American, and I much prefer BIDMAS. Was just supporting my favourite acronym out of the two.

ajholman

  • Posts: 253
Re: -5² = -25
« Reply #26 on: July 30, 2009, 05:48:54 pm »
Quote from: "Krask"
Incorrect. By putting -5² you are signifying that the minus sign is the operator. Whereas if you put (-5)², you would be swapping it so that the minus sign is to create a negative 5.

You only need to put brackets around a negative number if it might otherwise be a bit confusing:
-5 - -8 looks a bit easier to read as -5 - (-8)

If there is no potential for confusion then the brackets can be dispensed with. -5² is, completely unambiguously, 'negative five to the power of two'. It is an error to read it as 'zero minus 5 to the power of two'. If you want to write the latter, then write 0 - 5²

The potential for confusion comes from using the same symbol to mean two very different things: the operation 'minus' and the sign 'negative'.

edit: Well, it looks like you have a supporter, at least as far as using the brackets is concerned
http://mathforum.org/library/drmath/view/55713.html
It's interesting, I have never come across a situation where -5² would be interpreted as anything other than 'negative five to the power of two'. I'm going to ask a few colleagues to see how they would interpret it.

shadow

  • Woldean Court
  • Posts: 9455
Re: -5² = -25
« Reply #27 on: July 31, 2009, 12:54:12 pm »
dammit, this is the first time that I miss my admin powers!!!


my hands are itching to change the title to -(5)²=-25
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