## yasmeenabutineh Group Title 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? 2 years ago 2 years ago

1. dumbcow Group Title

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

2. dumbcow Group Title

n =6 a1 = 11 r = -4

3. dumbcow Group Title

does that make sense?

4. yasmeenabutineh Group Title

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

5. dumbcow Group Title

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

6. yasmeenabutineh Group Title

okay so -4^6-1?

7. dumbcow Group Title

yep

8. dumbcow Group Title

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