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Thread: How do you figure this out, can you help me please??

  1. #1
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    Question How do you figure this out, can you help me please??

    I have real problems trying to figure this out, as I was not in class when er learned this. Does anyone know how to??
    Ok so here is the question:

    21d*d+8d-26= 0

    What are the steps that you have to take???
    Thank you so much for helping me
    seetbinti
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  2. #2
    Forum Admin topsquark's Avatar
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    Quote Originally Posted by sweetbinti View Post
    I have real problems trying to figure this out, as I was not in class when er learned this. Does anyone know how to??
    Ok so here is the question:

    21d*d+8d-26= 0

    What are the steps that you have to take???
    Thank you so much for helping me
    seetbinti
    $\displaystyle 21d^2 + 8d - 26 = 0$

    The quickest approach is the quadratic formula.

    -Dan
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  3. #3
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    Quote Originally Posted by sweetbinti View Post
    I have real problems trying to figure this out, as I was not in class when er learned this. Does anyone know how to??
    Ok so here is the question:

    $\displaystyle 21d*d+8d-26= 0$

    What are the steps that you have to take???
    Thank you so much for helping me
    seetbinti
    $\displaystyle 21d*d+8d-26= 0 is also written as
    21d^2+8d-26= 0$


    now you can factorize this equation or as the above guy said use the quadratic formula, but assuming you don't know it I'll show you the factorizing method !!!


    so , $\displaystyle 21d^2 + 8d - 26 = 0$



    we can't split middle term so we do it by completing the square or by converting it to the form (a+b)^2 = 0

    so, we first transpose -26 to the RHS

    so we get

    $\displaystyle 21d^2 + 8d = 26$

    we no divide the whole equation by 21 to x^2 coefficient to a perfect square and 1 is a perfect square.

    so we get


    $\displaystyle d^2 + 8/21d = 26/21$

    can be written as


    $\displaystyle d^2 + 2(1)(4/21) = 26/21$

    no we add (4/21)^2 to both sides just to make the whole expression (a^2 + 2ab + b^2)ish

    so,

    $\displaystyle d^2 + 2+(1)(4/21) + (4/21)^2 = 26/21 + (4/21)^2$

    factorizing LHS we get


    $\displaystyle (d+4/21)^2 = 26/21 + 16/441$

    $\displaystyle (d+4/21)^2 = (546 + 16)/441$

    $\displaystyle (d+4/21)^2 = 562/441
    $
    $\displaystyle d+4/21$ = PLUS OR MINUS $\displaystyle Sqrt(562)/21$

    $\displaystyle d$ = PLUS OR MINUS$\displaystyle Sqrt(562)/21 - 4/21$

    and thats the solution.

    Ice Sync

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  4. #4
    A riddle wrapped in an enigma
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    Quote Originally Posted by topsquark View Post
    $\displaystyle 21d^2 + 8d - 26 = 0$

    The quickest approach is the quadratic formula.

    -Dan

    What he said!!

    $\displaystyle d=\frac{-4\pm\sqrt{562}}{21}$
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