If the sixth term of a sequence is 128 and the common ratio is 2, then what is the first term?

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(2) Answers

jasminemcdonald

first term = 4
second term = 4x2=8
3rd = 8x2 =16
4th = 16x2 = 32
5th = 32x2=64
6th = 64x2 = 128
answer: first term = 4

Genna57

common ratio mean geometric sequence
[latex]a_n=a_1(r)^{n-1}[/latex]
given tat r=2
and a6=128
[latex]a_6=a_1(2)^{6-1}=128[/latex]
[latex]128=a_1(2)^{5}[/latex]
[latex]128=a_1(32)[/latex]
divide both sides by 32
[latex]4=a_1[/latex]
the first term is 4