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Sequence 3 / 2,9 / 4,25 / 8,65 / 16. Find the first n terms and Sn
a(n)=(3/2)^n
S(n)=a(1)*[1-(3/2)^n]/(1-3/2)=3*[(3/2)^n-1]
The process of solving this problem: sequence 3 / 2, 9 / 4, 13 / 4, 65 / 16 The first n terms and?
3 / 2 = 1 + 1 / 2, 9 / 4 = 2 + 1 / 4, 13 / 4 = 3 + 1 / 8, the original formula = 1 + 2 + 3 + 4 +, + N + 1 / 2 + 1 / 4 + 1 / 8 +, + 1 / 2n power, then it's time for you to know, you have the wrong number of the third item, otherwise you don't have access to it
1.4.9.16.25.36.…… The 90th item of this sequence is ()
It's the square of the sequence n. 90 is 8100
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