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Math Help - factorising cubics

  1. #1
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    factorising cubics

    Can someone please explain to me the steps slowly how to factorise cubics??

    The question is Factorise (s^2 - 3s + 2)(s+4)
    And the answer is (s-1)(s-2)(s-4)

    I just don't get how they got from the first step to the last step.. Here's what I tried to do...

    s^3 + 4s^2 -3s^2 -12s + 2s +8
    s^3 + s^2 -10s + 8
    s(s^2 + s - 10) + 8
    And this is where i don't know what to do next ><

    Can someone please help me????
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  2. #2
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    Quote Originally Posted by gconfused View Post

    The question is Factorise (s^2 - 3s + 2)(s+4)
    The answer to this question is not


    Quote Originally Posted by gconfused View Post
    And the answer is (s-1)(s-2)(s-4)

    The answer is (s-1)(s-2)(s+4)

    This is because  s^2 - 3s + 2 = (s-1)(s-2)
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  3. #3
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    omigosh im so stupid ><.
    yeahh you're right, that is the answer haha i get it now
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  4. #4
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    Happy to help my fellow Aussie!
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  5. #5
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    One thing I keep telling students: If you have a problem that is already (partially) factored don't multiply it! Factoring is typically much harder than multiplying. If it is already factored for you, use that!
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