Question

What is the sum of a 6-term geometric sequence if the first term is 11, the last term is –11,264 and the common ratio is –4?

Answer 1

\[\large s_{n} = \frac{a_{1}(r^{n}-1)}{r-1}\]

Answer 2

n =6
a1 = 11
r = -4

Answer 3

does that make sense?

Answer 4

sn=11(-4-1)/-4-1?

Answer 5

yes except the " -4" on top should be raised to the 6th power

Answer 6

okay so -4^6-1?

Answer 7

yep

Answer 8

make sure you include the negative sign when raising to power.....-4^6 is different than (-4)^6