85.4k views
1 vote
__,__,80,64,51.2,40,96,...

Find the first two terms of the geometric sequence.

2 Answers

5 votes

Answer:

125, 100, 80,64,51.2,40.96...

Explanation:

y=
(4)/(5)x

So let's work backwards!


(5)/(4)(80)

=100

Then...


(5)/(4)(100)

=125

Hope this helps! :D

User Ramtin Gh
by
8.5k points
4 votes

Answer:

125, 100

Explanation:

Perhaps the terms of your series are supposed to be ...

__, __, 80, 64, 51.2, 40.96, ...

The common ratio is 64/80 = 0.8, so the recursive relation is ...

t[n] = 0.8×t[n-1]

__

Solving for the previous term, we find ...

t[n]/0.8 = t[n-1] . . . . . . divide by 0.8

or ...

t[n-1] = 1.25×t[n] . . . . . rearrange

Then the term previous to 80 is 1.25×80 = 100.

And the term previous to 100 is 1.25×100 = 125.

The first two terms of the geometric sequence are 125 and 100.

User Daniel Kamil Kozar
by
8.2k points

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