Math Algebra

The first term of a geometric progression is more than the third term by 12. The fourth term is more than the second term by 4. Find:
i.the first term a and the common ratio r.
ii. the n'th term of the progression.

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asked by Leda
  1. Geometric Progression: x(n) = a r^n
    First term x(0) = a
    Second term x(1) = ar
    etc.
    So
    a = ar^2 +12
    ar^3 = ar +4
    Rearranging gives,
    a(1-r^2) = 12
    a(1-r^2)r = -4
    Thus solve for r by dividing,

    Substitute into the original to solve for a,

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    posted by Graham
  2. Omg im really sorry. There seems to be an error. The "fifth" term of a geometric progression is more than the third term by 12.

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    posted by Leda

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