Question

what is the sum of the geometric sequence -4, 24, -144 if there are 8 terms

Answer 1

@timo86m @DAMONSANCHEZ @dinisha

Answer 2

first we find the common ratio by dividing the 2nd term by the first term.
24 / -4 = -6
so our common ratio is -6

now we use the sum formula :
sn = a1 (1 - r^n) / (1 - r)
n = sum of the terms we want to find = 8
a1 = first term = -4
r = common ratio = -6
now we sub
s8 = -4 (1 - (-6^8) / (1 - (-6)
s8 = -4 (1 + 1679616) / (1 + 6)
s8 = -4 (1679616) / 7
s8 = - 6718464/7
s8 = -959781

Answer 3

life saver thank you! can u help with another please please

Answer 4

I can try

Answer 5

what are the explicit equation and domain for a geometric sequence with a first term of 4 and a second term of -8

Answer 6

explicit equation :
an = a1 (r ^ n -1)
a1 = 4
r = -8/4 = -2
now sub
an = 4 (-2^n-1)

I do not know hw to do the domain

Answer 7

ok thanks.. maybe u can do antoher one