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Math Help - [SOLVED] I need my answers checked.

  1. #1
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    [SOLVED] I need my answers checked.

    The following questions came with only one instruction: simplify.


    question #1:(x+2)(x+3)
    My answer:x^2+5

    Question #2: (2x-5)(3x+2)
    My answer: 5x-3

    Question #3: (2x+5)(x^2-x-2)
    2x(2^2-x-2)+5(x^2-x-2)


    Thanks in advance for your help!

    Drakmord
    Last edited by mr fantastic; July 31st 2009 at 10:48 PM. Reason: Diasbled smilies so that brackets worked.
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  2. #2
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    Quote Originally Posted by drakmord View Post
    The following questions came with only one instruction: simplify.


    question #1: (x+2)(x+3)
    My answer:x^2+5
    Wrong.

    Question #2: (2x-5)(3x+2)
    My answer: 5x-3
    Wrong.

    Question #3: (2x+5)(x^2-x-2)
    2x(2^2-x-2)+5(x^2-x-2)
    A good start but not finished.


    Thanks in advance for your help!

    Drakmord
    How about showing HOW you got those answers so we can make suggestions to correct them.
    Last edited by mr fantastic; July 31st 2009 at 10:50 PM. Reason: Added quote tag for third quote. And disabled smilies so that brackets worked in first quote
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  3. #3
    Senior Member Stroodle's Avatar
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    Here's a good place to learn how to do these: Simple Polynomial Multiplication
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  4. #4
    A riddle wrapped in an enigma
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    Quote Originally Posted by drakmord View Post
    The following questions came with only one instruction: simplify.


    question #1: (x+2)(x+3)
    My answer:x^2+5

    Question #2: (2x-5)(3x+2)
    My answer: 5x-3

    Question #3: (2x+5)(x^2-x-2)
    2x(x^2-x-2)+5(x^2-x-2) ====> I corrected your type here.


    Thanks in advance for your help!

    Drakmord
    Hi drakmord,

    Do #1 and #2 the same way as you started doing #3, but complete the job as Hallsofivy suggested. You need to complete the distribution and combine like terms.

    Also, the site that Stroodle gave you is a good one. It appears that in #1 and #2 you are having a little trouble deciding if you should be multiplying or adding. Did you state them correctly? If you did, then you should be multiplying.

    Last edited by mr fantastic; July 31st 2009 at 10:50 PM.
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  5. #5
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    Hi there,

    I believe your working should look something like this:

    (x+2)(x+3)= x(x+3) + 2(x+3) = x^2 + 3x + 2x + 6 = x^2 + 5x + 6

    (2x-5)(3x+2) = 2x(3x+2) -5(3x +2) = 6x^2 + 4x -15x -10 = 6x^2 -11x -10

    (2x+5)(x^2-x-2) = 2x(x^2-x-2)+5(x^2-x-2)= 2x^3-2x^2-4x+5x^2-5x-10 = 2x^3+3x^2-9x-10

    Cheers
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  6. #6
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    Thank you so much for the assist guys!

    Quote Originally Posted by Joel View Post
    Hi there,

    I believe your working should look something like this:

    (x+2)(x+3)= x(x+3) + 2(x+3) = x^2 + 3x + 2x + 6 = x^2 + 5x + 6

    (2x-5)(3x+2) = 2x(3x+2) -5(3x +2) = 6x^2 + 4x -15x -10 = 6x^2 -11x -10

    (2x+5)(x^2-x-2) = 2x(x^2-x-2)+5(x^2-x-2)= 2x^3-2x^2-4x+5x^2-5x-10 = 2x^3+3x^2-9x-10

    Cheers
    Thanks for that I can see where I went wrong, I used FOIL but did not finish the job.

    drakmord
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