Question

@Miracrown

Answer 1

Is it A?

Answer 2

What makes you think its A?

Answer 3

Well you should do the calculations to be sure.

Answer 4

Well I used wolfram alpha and I got A. But I'm not sure if I plugged it in right. Can you check please?

Answer 5

I am crunching sum numbs wait a min

Answer 6

\[
\sum_{k=0}^nar^k=\frac{a\left(r^{n+1}-1\right)}{r-1}
\]

Answer 7

I calculated it a couple times to check, and I don't get A
We'll need this formula:
\[S _{n} \space =a _{1} \frac{ (1-r ^{n}) }{ (1-r)}\]

Then ...
\[= 2\space \frac{ (1-(-2)^{7}) }{ (1-(-2))}\]

Do you see anything we can simplify there?

Answer 8

Yes, we can simplify the 1s and the -2s

Answer 9

Right, so the two minus signs cancel

Answer 10

\[=2 \space \frac{ (1-(-2)^7) }{ 3 }\]

Answer 11

Then we can evaluate (-2)^7 What does that equal?

Answer 12

-128

Answer 13

I agree wid u

Answer 14

\[= 2 \space \frac{ (1-(-128)) }{ 3 }\]
What should we do then?

Answer 15

See why calculating is important? It's not going to be negative.

Answer 16

2 129/3
2 (43)
86 is the answer

Answer 17

Yep.

Answer 18

It was a different question @Miracrown

Answer 19

thank you!

Answer 20

I was mistaken.

Answer 21

All good