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The first term of a geometric sequence is 25, and the fourth term is 1\5.

(a) Find the common ratio r.
r =

Find the fifth term.
a5 =

(b) Find the partial sum of the first eight terms.
S8 =

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1 answer

  1. r^3 = (1/5)/25 = 1/125
    so, r = 1/5

    An = 5*(1/5)^(n-1) = 125/5^n

    S8 = 25(1 - (1/5)^8)/(1 - 1/5) = 97656/3125

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