Question

Find S9 for the series 1 + 5 + 25 + 125 +...
i cnt be anything? bc i got 0

Answer 1

it is a geometric sequence whose first term is a1= 1 and constant q is 5

Answer 2

okay

Answer 3

so:
\[\Large {S_9} = {a_1}\frac{{1 - {q^9}}}{{1 - q}} = 1 \cdot \frac{{1 - {5^9}}}{{1 - 5}} = ...?\]

Answer 4

488281

Answer 5

that's right!

Answer 6

Find S10 for the series 1 + 2 + 4 + 8 +... is it the same formula if its not mulitpying by 2?

Answer 7

here we have:
first term= 1
constant= 2
so:
\[\Large {S_{10}} = {a_1}\frac{{1 - {q^{10}}}}{{1 - q}} = 1 \cdot \frac{{1 - {2^{10}}}}{{1 - 2}} = ...?\]

Answer 8

1023

Answer 9

correct!