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Math Help - Solving Equations by factoring

  1. #1
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    Solving Equations by factoring

    I'm stuck in the highlighted part of the problem....
    Attached Thumbnails Attached Thumbnails Solving Equations by factoring-image.jpg  
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  2. #2
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    Re: Solving Equations by factoring

    Quote Originally Posted by asilvester635 View Post
    I'm stuck in the highlighted part of the problem....
    "I'm stuck" what do you mean by that.
    As written there is nothing else to be done with that question.

    Did you fail to post the entire question?
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    Re: Solving Equations by factoring

    Quote Originally Posted by asilvester635 View Post
    I'm stuck in the highlighted part of the problem....
    Watch the sign of 24z in the third line. Why you omitted = 0?
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  4. #4
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    Re: Solving Equations by factoring

    I believe that the you can not factor 4z(z^2 - z + 6) any further... Also you are missing a negative sign before 4z
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    Re: Solving Equations by factoring

    There is no reason to believe there was an "= 0" to be omitted! The difficulty is that asilvester635 has not told us what the problem is or what he is trying to do.
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    Re: Solving Equations by factoring

    Quote Originally Posted by HallsofIvy View Post
    There is no reason to believe there was an "= 0" to be omitted! The difficulty is that asilvester635 has not told us what the problem is or what he is trying to do.
    There is = sign in the first line.
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  7. #7
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    Re: Solving Equations by factoring

    I did not see that! Thank you.
    asilvester635, your first line was 4z^3= 4z^2+ 24z. Your next line should be -4z^3+ 4z^2+ 24z= 0 (you have subtracted 4z^3 from both sides). But then you have " 4z^3- 4z^2+ 24z". My guess is that you intended to multiply by -1 but, again, you must have "= 0" and you did not multiply the "24z" by -1. You should have 4z^3- 4z^2- 24z= 0. Obviously both "4" and "z" divide each term so you can factor 4z out: 4z(z^2- z- 6)= 0. (3)(2)= 6 and their difference is 1 so we can further factor as 4z(z- 3)(z+ 2)= 0.

    Now what? Remember the basic reason for factoring: "if ab= 0 then either a= 0 or b= 0".
    Last edited by HallsofIvy; September 24th 2013 at 06:39 AM.
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