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Factorise please

  1. Oct 15, 2013 #1
    Factorise this expression:
    12x to power of 2 minus 27x to power of 2.

    I have tried to factorise this using two brackets but I could't work it out.
    For example:
    (3x-4y)(4x+8y) or (2x-4y)(6x+7y) will not work because there is no third number in the expression.
    There as I think this should be alright:
    3(4x to power of two - 9y to power of two)
    Am I right?
     
  2. jcsd
  3. Oct 15, 2013 #2

    SteamKing

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    Staff Emeritus
    Science Advisor
    Homework Helper

    You have, I think, (12x)^2 - (27x)^2

    When you factor out a constant from this expression, the constant must be squared.

    is 12^2 = 3*4^2?
    or is 12^2 = 3^2*4*^2?
     
  4. Oct 15, 2013 #3

    Ray Vickson

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    Science Advisor
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    You wrote that you want to factorize ##(12x)^2 - (27x)^2.## Is that what you really want, or did you mean ##12 x^2 - 27 x^2##? You can write these out in text as (12x)^2 - (27x)^2 in the first case and as 12 x^2 - 27 x^2 in the second case. No need to write out ""to power of 2"---just use ^, or use the X2 button on the input pallette; it gives you (12x)2 - (27x)2, for example.
     
  5. Oct 15, 2013 #4
    I have 12x^2-27x^2
    Now what?
     
  6. Oct 15, 2013 #5

    Mark44

    Staff: Mentor

    Is there some reason you didn't use the homework template?
     
  7. Oct 15, 2013 #6
    What do you mean by homework template?
     
  8. Oct 15, 2013 #7

    Mark44

    Staff: Mentor

    When you started the thread, didn't you see a template with three parts (problem description, relevant equations, your efforts)? If you are using PF on a phone, the template might not appear.
     
  9. Oct 15, 2013 #8
    I am in fact using my phone, I have done what you said, I still have no idea of the template, and still not getting the answer yet!!!!!
     
  10. Oct 15, 2013 #9

    Mark44

    Staff: Mentor

    What factors do 12x2 and -27x2 have in common (i.e., that both have)?
     
  11. Oct 15, 2013 #10
    They both 3 in common
    3x9=27
    3x4=12
     
  12. Oct 15, 2013 #11
    They both have 3 in common
     
  13. Oct 15, 2013 #12

    Mark44

    Staff: Mentor

    They both have something else in common.
     
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