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Find an explicit rule for the nth term of a geometric sequence where the second and fifth terms are -36 and 2304, respectively

User Slonkar
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1 Answer

3 votes

a_5=ra_4=r^2a_3=r^3a_2

2304=-36r^3\implies r=-4

Since
a_2=ra_1\implies -36=-4a_1\implies a_1=9, the sequence takes the form


a_n=(-4)^(n-1)a_1=9(-4)^(n-1)
User Ashley Baldry
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