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Math Help - Solving an algerbraic equation.

  1. #1
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    Solving an algerbraic equation.

    Hi all.
    I got this question from my example booklet, which has the question worked. However, im not quite sure how the problem is solved, and i cant follow how the exmaple booklet does it.

    If someone could break down the steps for me that would be amazing.

    This is what the booklets steps are:

    -300 = 0 + (1/2) * (-9.8) * t^2

    t^2 = -300 * 2 / -9.8

    t^2=61.22

    hence, t = 7.8s


    I dont understand how it goes from the first line to the second one.

    Any help would be greatly appreciated.
    Thanks.
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  2. #2
    Behold, the power of SARDINES!
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    Quote Originally Posted by FlexedCookie View Post
    Hi all.
    I got this question from my example booklet, which has the question worked. However, im not quite sure how the problem is solved, and i cant follow how the exmaple booklet does it.

    If someone could break down the steps for me that would be amazing.


    This is what the booklets steps are:

    -300 = 0 + (1/2) * (-9.8) * t^2

    t^2 = -300 * 2 / -9.8

    t^2=61.22

    hence, t = 7.8s


    I dont understand how it goes from the first line to the second one.

    Any help would be greatly appreciated.
    Thanks.
    \displaystyle -300=0+\frac{1}{2}(-9.8)t^2 step 1 simplify this gives

    \displaystyle -300=\frac{-9.8}{2}t^2 Isolate the variable by multiplying both sides of the equation by the reciprocal of the fraction

    \displaystyle -300\left(\frac{2}{-9.8}\right)=\left( \frac{2}{-9.8}\right)\frac{-9.8}{2}t^2 Simplify both sides

    \displaystyle \frac{600}{9.8}=t^2 Now take the square root of both sdies

    \displaystyle \sqrt{\frac{600}{9.8}}=\sqrt{t^2} \implies \sqrt{\frac{600}{9.8}}=t

    Now just put the last bit into a calculator

    \displaystyle t=\sqrt{\frac{600}{9.8}} \approx \sqrt{61.2244} \approx 7.82
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  3. #3
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    Thank you so much
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  4. #4
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    Quote Originally Posted by FlexedCookie View Post
    -300 = 0 + (1/2) * (-9.8) * t^2

    t^2 = -300 * 2 / -9.8

    t^2=61.22

    hence, t = 7.8s

    Well, that's sure a confusing way to solve something simple;
    why not do the multiplication FIRST:
    -300 = -4.9 t^2 ; then:
    t^2 = 300 / 4.9
    t = SQRT(300 / 4.9)
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  5. #5
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    Quote Originally Posted by Wilmer View Post
    Well, that's sure a confusing way to solve something simple;
    why not do the multiplication FIRST:
    -300 = -4.9 t^2 ; then:
    t^2 = 300 / 4.9
    t = SQRT(300 / 4.9)

    How did you get the positive 4.9? I can only manage to get a postive 300 and a negative 4.9 before the square root...
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  6. #6
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    \frac{-300}{-4.9}= \frac{300}{4.9}. How did you get the numerator positive and the denominator negative?
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  7. #7
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    Ahahaha dont ask... i may or may not have dont the equation completely wrong. I understand the first solution, but not the second one posted.
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  8. #8
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    You don't understand that:
    -300 = -4.9 t^2
    t^2 = -300 / -4.9
    t^2 = 300 / 4.9
    ??
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