Question

is my answer correct?

Answer 1

@Lord_Box

Answer 2

@ganeshie8

Answer 3

Yes.
common difference can be obtained by subtracting any present term from its next term :

\[2-5 = -1-2 = -3\]

Answer 4

Good job

Answer 5

can you check some more for me?

Answer 6

I'll try

Answer 7

your help is very much appreciated

Answer 8

I think the domain is all integers n >= 1

Answer 9

but 1 works doesn't it ?

Answer 10

Depends on your teacher, but that is what most textbooks follow.

Answer 11

greater than or equal to one or just greater then

Answer 12

oh wait nvm i see now

Answer 13

good, the sequence usually starts with n = 1

Answer 14

cause negative numbers would not work correct

Answer 15

how about this one

Answer 16

sorry i just need tog get an a on this and this was a hard lesson for me

Answer 17

They work perfectly! Its just that it looks nice if we start the sequence from n=1.
Let me ask you a question

Answer 18

okay

Answer 19

I'll ask in the end, let's look at your latest q

Answer 20

May I know how you got that answer ?

Answer 21

but if you plug negative one into that equation, you get -12?

Answer 22

That's okay. I'm asking about your latest question on geometric series

Answer 23

= 6(1 - 4^7)/(1 - 4)
= 6(-16383)/(-3)
= 32,766

Answer 24

oh haha would it be positive

Answer 25

Yes! We could have avoided all that calculation if we had looked at the options and used some commonsense

Answer 26

You have first term = 6
last term = 24576


add them, what do you get ?

Answer 27

You get something more than 20 thousand, right ?

Answer 28

the common ratio is 4, which is positive.

Answer 29

So the sum of the geometric series will be greater than 20 thousand

Answer 30

okay ahh i got you

Answer 31

You may save the amount of work that needs to be done sometimes. But I prefer your method as it always gives you the correct answer!

Answer 32

pretty confident on this one

Answer 33

again thank you so much you're very helpful

Answer 34

Looks perfect!
http://www.wolframalpha.com/input/?i=21*(1-9%5E6)%2F(1-9)

Answer 35

i have one i have no idea how to go about

Answer 36

google for infinite geometric series formula

Answer 37

Hey no, wait.

Answer 38

The common ratio is 3, which is greater than 1. So the series blows up like crazy

Answer 39

It doesn't converge.

Answer 40

so divergent?

Answer 41

Yep

Answer 42

Given the geometric sequence where a1 = −1 and the common ratio is 7, what is the domain for n?

this would be a greater than or equal to -1 correct

Answer 43

No

Answer 44

sigh im confused

Answer 45

domain has nothing to do with the terms in the sequence

Answer 46

so 1 again?

Answer 47

domain is simply the values of the index "n"

Answer 48

Yes, domain is all integers n >= 1

Answer 49

when n = 1, you have a1 = -1

Answer 50

okay gotcha

Answer 51

Look at the dots in the given diagram

Answer 52

Can you put those 3 dots on a single straight line ?

Answer 53

no

Answer 54

I think below is a better way to ask :

Can you draw a single straight line through those 3 dots ?

Answer 55

well not a straight line i don't believe

Answer 56

only through2

Answer 57

We missed the third point. It is not possible to draw a straight line through those points.

Answer 58

So that sequence CANNOT be an "arithmetic sequence"

Answer 59

so then what would i put

Answer 60

What other options do you have ?

Answer 61

none that is all

Answer 62

Find the common ratio

Answer 63

first term = 3
second term = 0.6

common ratio, r = ?

Answer 64

5?

Answer 65

No, try again

Answer 66

1/5?

Answer 67

common ratio = (next term)/(present term) = 0.6/3 = 6/30 = 1/5

Answer 68

Yes

Answer 69

so either a or d

Answer 70

If the first term is \(a_1\) and the common ratio is \(r\), then the general term is given by

\[a_n = a_1 (r)^{n-1}\]

Answer 71

how do i find first term

Answer 72

would it be 3?

Answer 73

Yes

Answer 74

so a ?

Answer 75

Yes!

Answer 76

cool! still down to help with a couple more? I'm almost done and its helping me understand

Answer 77

This thread is lagging. Could you post in a new thread and tag me ?

Answer 78

yes!