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Math Help - factorising

  1. #1
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    Question factorising

    hey, i'm finding it difficult how to factorise this equation:

    t - 3t + 4 = 0

    i've found out the answer already, but i really dont understand how i would get the answer- It would be very helpful if someone could give me a step to step guide on how to get to the answer.

    lolz..i've used the word answer so many times in this thread but i don't want to give it away incase some MHF users would like to solve the question themselves.
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  2. #2
    A riddle wrapped in an enigma
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    Quote Originally Posted by ladythugette View Post
    hey, i'm finding it difficult how to factorise this equation:

    t - 3t + 4 = 0

    i've found out the answer already, but i really dont understand how i would get the answer- It would be very helpful if someone could give me a step to step guide on how to get to the answer.

    lolz..i've used the word answer so many times in this thread but i don't want to give it away incase some MHF users would like to solve the question themselves.
    Hi ladythugette,

    You know, by the Rational zeros theorem, that if it has any rational roots at all,
    they will be +/- the factors of 4.

    I tried 2 and found that to be a zero, and used synthetic division to find the other two.

    Code:
     
    2 | 1 -3  0  4
           2 -2 -4
       ---------------
        1 -1 -2  0
    The depressed polynominal is now a quadratic: x^2-x-2 and can easily be factored.
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  3. #3
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    i've never heard of the rationals zero theorem before.i'm trying to understand what you mean but my brain seems to working very slow today.is there an alternative method that could be used to work out this question? or if not, could you explain the rationals zero theorem to me again please.
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  4. #4
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    Quote Originally Posted by ladythugette View Post
    i've never heard of the rationals zero theorem before.i'm trying to understand what you mean but my brain seems to working very slow today.is there an alternative method that could be used to work out this question? or if not, could you explain the rationals zero theorem to me again please.
    here is an explanation from the beginning ...

    The Rational Roots Test
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  5. #5
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    Quote Originally Posted by ladythugette View Post
    hey, i'm finding it difficult how to factorise this equation:

    t - 3t + 4 = 0

    i've found out the answer already, but i really dont understand how i would get the answer- It would be very helpful if someone could give me a step to step guide on how to get to the answer.

    lolz..i've used the word answer so many times in this thread but i don't want to give it away incase some MHF users would like to solve the question themselves.
    a way you could do this is to look for similar factors for example in this case:
    t - 3t + 4 = 0
    u could rewrite the equation as t + 1 - 3t + 3 = 0
    now t + 1 = (t + 1)(t - t + 1) and -3t + 3=-3(t - 1)=-3(t - 1)(t + 1).
    As you can see we have same factors so we can write the equation as
    (t + 1)[t - t + 1 - 3(t - 1)]=(t + 1)(t - 4t + 4)=(t + 1)(t - 2)=(t + 1)(t - 2)(t - 2)
    So there's the solution.
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