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Math Help - SAT Problem

  1. #1
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    SAT Problem

    If g(x) = x * 2^x, then g(a+1) - g(a)=
    (a) (a+2)2^a
    (b) (2a+1)2^a
    (c) (2a-1)2^1
    (d) (a+1)2^a+1
    (e) (a)2^a+1
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  2. #2
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    Quote Originally Posted by juliak View Post
    If g(x) = x * 2^x, then g(a+1) - g(a)=
    (a) (a+2)2^a
    (b) (2a+1)2^a
    (c) (2a-1)2^1
    (d) (a+1)2^a+1
    (e) (a)2^a+1
    Try some values for a and see which cases are possible. For example if a=0

    g(a+1)-g(a)=g(1)-g(0)=2

    and (a)=2, (b)=1, (c)=-2, (d)=2, (e)=1

    so we have elliminated all but (a) and (d), now try another value.

    CB
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  3. #3
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    Thank you very very much!

    (sorry but) another question I have:

    Which of the following CANNOT represent the degree measure of an equiangular polygon?
    (a) 165
    (b) 162
    (c) 140
    (d) 125
    (e) 90
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  4. #4
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    Quote Originally Posted by juliak View Post
    Thank you very very much!

    (sorry but) another question I have:

    Which of the following CANNOT represent the degree measure of an equiangular polygon?
    (a) 165
    (b) 162
    (c) 140
    (d) 125
    (e) 90
    The internal sum of a polygon is given by (n - 2)180^\circ, where n is the number of sides.

    If it is a regular polygon then all the angles are equal. Since you have n angles, then if \theta is one of the angles

    n\theta = (n - 2)180^\circ.

    So \theta = \frac{(n - 2)180^\circ}{n}.


    So now substitute some values for n and see which ones that you have listed apply.
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