Question

Find the sum of a finite geometric sequence from n = 1 to n = 6, using the expression −2(5)^(n − 1)

Answer 1

−2(5)^(n − 1)

compare it with \(\Large a_1 r^{n-1}\)

you will get a1 and r

Answer 2

a1=-2 and r=5

Answer 3

then use the sum formula \(\Large S_n =a_1 \dfrac{r^n-1}{r-1} \)

Answer 4

Sn=-2(5^(n)-1/5-1)?

Answer 5

sorry my equation button isn't working at the moment

Answer 6

no problem
and thats correct
simplify that

Answer 7

plug in n=6
because u need sum of 6 terms

Answer 8

so Sn=-2(5^(6)-1/5-1?

Answer 9

-2 [(5^6 -1)/ (5-1)]

Answer 10

yes that

Answer 11

simplify it

Answer 12

-2*(3906)

Answer 13

-7812

Answer 14

\(\huge \checkmark \)

Answer 15

yay thank you so much!