Question
Write the first five terms of the sequence and obtain the corresponding series a1 = 3, an = 3an-1 + 2 for all n > 1

Answer

Given: a1 = 3, an-1 + 2 for all n > 1

Putting n = 2, 3, 4 and 5, we get

a2 = 3a2-1 + 2 = 3a2-1 + 2 = 3a1 + 2 = 3 $\times$ 3 + 2 = 9 + 2 = 11

a3 = 3a3-1 + 2 = 3a2 + 2 = 3 $\times$ 11 + 2 = 33 + 2 = 35

a4 = 3a4-1 + 2 = 3a3 + 2 = 3 $\times$ 35 + 2 = 105 + 2 = 107

a5  3a5-1 + 2 = 3a4 + 2 = 3 $\times$ 107 + 2 = 321 + 2 = 323

Hence the first five terms are 3,11,35,107,323.

Therefore, corresponding series is 3 + 11 + 35 + 107 + 323 + ……….

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