Welcome! Check out our free B-School Guides to learn how you compare with other applicants.
Login or Register
 

Negative Number Raised to a Power

This topic has 2 expert replies and 5 member replies
Bookmark
Previous Topic Next Topic
BlindVision Really wants to Beat The GMAT!
Joined
26 Dec 2008
Posted:
253 messages
Followed by:
1 members
Thanked:
8 times
Target GMAT Score:
700+
Negative Number Raised to a Power Post Mon Mar 23, 2009 4:42 pm
Elapsed Time: 00:00
  • Lap #[LAPCOUNT] ([LAPTIME])
    Can someone refresh me on a rule or illustrate the logic that a negative number raised to any power still yields a negative answer?

    examples:

    -2^2 = -4

    -2^5 = -32

    -3^2 = -9

    -3^3 = -27

    Need free GMAT or MBA advice from an expert? Register for Beat The GMAT now and post your question in these forums!
    cramya GMAT Titan Default Avatar
    Joined
    28 Aug 2008
    Posted:
    2469 messages
    Followed by:
    7 members
    Thanked:
    318 times
    Post Mon Mar 23, 2009 4:59 pm
    (negative integer) raised to (even positive power) is positive.


    (-2) ^ 2 = 4 (not -4 as stated above)

    (-2) ^ 4 = 16

    (negative integer) raised to (odd positive power) is negative

    (-2)^3 = -8
    (-2)^1 = -2

    Hope this helps.



    Last edited by cramya on Tue Mar 24, 2009 5:38 pm; edited 2 times in total

    Thanked by: BlindVision
    Bhattu Just gettin' started! Default Avatar
    Joined
    05 Apr 2007
    Posted:
    21 messages
    Thanked:
    2 times
    Test Date:
    26/03/09
    Target GMAT Score:
    720
    GMAT Score:
    600
    Post Tue Mar 24, 2009 2:00 am
    cramya wrote:
    (negative integer) raised to (even positive power) is positive.


    -2 ^ 2 = 4 (not -4 as stated above)

    -2 ^ 4 = 16

    (negative integer) raised to (odd positive power) is positive.

    -2^3 = -8
    -2^1 = -2

    Hope this helps.
    I think there was a typo, shouldn't it be = (negative integer) raised to (odd positive power) is negative?

    GMAT/MBA Expert

    Ian Stewart GMAT Instructor
    Joined
    02 Jun 2008
    Posted:
    2178 messages
    Followed by:
    245 members
    Thanked:
    951 times
    GMAT Score:
    780
    Post Tue Mar 24, 2009 9:28 am
    cramya wrote:
    (negative integer) raised to (even positive power) is positive.

    -2 ^ 2 = 4 (not -4 as stated above)
    Here, it really depends on how the expression is written. If you raise -2 to the power of 2, the answer is certainly positive 4. That is, if you have:

    (-2)^2

    that is equal to 4, because this is equal to (-2)*(-2). However, if the negative is not enclosed in brackets, as was written in the original post:

    -2^2

    then by order of operations (BEDMAS), we must raise 2 to the power 2 first, then take the negative of that. So, if there are no brackets,

    -2^2 = -4

    because this is equal to -(2)*(2).

    _________________
    Nov 2011: After years of development, I am now making my advanced Quant books and high-level problem sets available for sale. Contact me at ianstewartgmat at gmail.com for details.

    private GMAT tutor in Toronto

    Thanked by: BlindVision
    Bhattu Just gettin' started! Default Avatar
    Joined
    05 Apr 2007
    Posted:
    21 messages
    Thanked:
    2 times
    Test Date:
    26/03/09
    Target GMAT Score:
    720
    GMAT Score:
    600
    Post Tue Mar 24, 2009 10:11 am
    Thanks for that - helps clarify that for me and also probably a careless error I should be aware of

    BlindVision Really wants to Beat The GMAT!
    Joined
    26 Dec 2008
    Posted:
    253 messages
    Followed by:
    1 members
    Thanked:
    8 times
    Target GMAT Score:
    700+
    Post Tue Mar 24, 2009 10:23 am
    Ian Stewart wrote:
    then by order of operations (BEDMAS), we must raise 2 to the power 2 first, then take the negative of that. So, if there are no brackets,

    -2^2 = -4

    because this is equal to -(2)*(2).
    What does the "B" in "BEDMAS" stand for? "Brackets"? Thank you!

    GMAT/MBA Expert

    Ian Stewart GMAT Instructor
    Joined
    02 Jun 2008
    Posted:
    2178 messages
    Followed by:
    245 members
    Thanked:
    951 times
    GMAT Score:
    780
    Post Tue Mar 24, 2009 11:12 am
    BlindVision wrote:
    Ian Stewart wrote:
    then by order of operations (BEDMAS), we must raise 2 to the power 2 first, then take the negative of that. So, if there are no brackets,

    -2^2 = -4

    because this is equal to -(2)*(2).
    What does the "B" in "BEDMAS" stand for? "Brackets"? Thank you!
    Yes, 'brackets'. The mnemonic is sometimes presented as 'PEDMAS', where the P stands for 'parentheses'.

    _________________
    Nov 2011: After years of development, I am now making my advanced Quant books and high-level problem sets available for sale. Contact me at ianstewartgmat at gmail.com for details.

    private GMAT tutor in Toronto

    Thanked by: BlindVision
    cramya GMAT Titan Default Avatar
    Joined
    28 Aug 2008
    Posted:
    2469 messages
    Followed by:
    7 members
    Thanked:
    318 times
    Post Tue Mar 24, 2009 5:38 pm
    Thanks Ian.


    Bhattu, I have corrected the typo.

    Regards,
    CR

    Best Conversation Starters
    1 varun289 31 topics
    2 sana.noor 24 topics
    3 killerdrummer 21 topics
    4 Rudy414 19 topics
    5 guerrero 15 topics
    See More Top Beat The GMAT Members...

    Most Active Experts
    1 image description Brent@GMATPrepNow

    GMAT Prep Now Teacher

    		 198 posts
    2 image description GMATGuruNY

    The Princeton Review Teacher

    		 135 posts
    3 image description Jim@StratusPrep

    Stratus Prep

    		 106 posts
    4 image description Anju@Gurome

    Gurome

    		 41 posts
    5 image description David@VeritasPrep

    Veritas Prep

    		 40 posts
    See More Top Beat The GMAT Experts