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Math Help - Final Questions for Practice Test

  1. #1
    MHF Contributor
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    Final Questions for Practice Test

    Find the equation of the tangent line for the function f(x) = x^2 + 1 at point (3, 10).

    A. y = 6x - 8

    B. y = -6x+8

    C. y = 6x+8

    D. None of these


    Question 14.

    If I divide my eldest cousin's age by 3 and subtract 4, i get the same result as when I divide his age by 6. What is his cousin's age?



    A. 22yrs

    B. 24yrs

    C. 30yrs

    D. None of these
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  2. #2
    Newbie
    Joined
    Nov 2009
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    Question:

    If we have the function f(x) = x^2 + 1 our derivative would be f'(x) = 2x. If we need our slope at point (3, 10) we plug the x into our derivative, we get: f'(3) = 2 \cdot 3 . Which results in 6.

    Now we need to find some equation that crosses the point (3, 10) with the following form y(x) = ax + b, we can do this by plugging in our coordinates and our slope: 10 = 3 \cdot 6 + b, which gives us: -8. Our equation would look like: y(x) = 6x - 8. Which is A.

    Question 14:

    I would say he is 24. Because \frac{x}{3} - 4 = \frac{x}{6}.

    Now solve the equation for x:

    \frac{x \cdot 2}{3 \cdot 2} - \frac{4 \cdot 6}{6} = \frac{x}{6} (note: I'm doing this so our denominator is the same on both sides)

    2x - 24 = x

     2x - x = 24

    x = 24

    Correct answer would be B.
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