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Thread: More to come from me !! Itís been a while

  1. #1
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    More to come from me !! Itís been a while

    Solve a^2 - 7a - 30 = 0
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  2. #2
    MHF Contributor MarkFL's Avatar
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    Re: More to come from me !! Itís been a while

    I would factor here...can you name two factors of -30 whose sum is -7?
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    Re: More to come from me !! Itís been a while

    Oh I see, it is -10 and 3, but than my question is what is done with the 0 after the GCF is found
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    Re: More to come from me !! Itís been a while

    Also, what happens to the a in 7a?
    Last edited by Eddyrodriguez; Jun 17th 2018 at 11:13 AM.
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    MHF Contributor MarkFL's Avatar
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    Re: More to come from me !! Itís been a while

    Quote Originally Posted by Eddyrodriguez View Post
    Oh I see, it is -10 and 3, but than my question is what is done with the 0 after the GCF is found
    Yes, and so we may write:

    $\displaystyle a^2-7a-30=(a-10)(a+3)=0$

    Now, equate each factor to zero, and solve for a to get the two roots.
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  6. #6
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    Re: More to come from me !! Itís been a while

    The basic point in solving problems like this is the "zero product property": "if ab= 0 then either a= 0 or b= 0". Once you have that $\displaystyle (a- 10)(a+ 3)= 0$ then we must have either $\displaystyle a- 10= 0$ or $\displaystyle a+ 3= 0$. That gives, of course, two different values for a either of which satisfies the original equation.
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