Question

What is the sum of the first n terms of this sequence? 3,4,5,6,7...

Answer 1

I'll give a medal and fan :)

Answer 2

you know the difference right?
For how many terms do you need the sum ?

Answer 3

(last term + first term) times (number of terms / 2 )

for any arithmetic sequence.

Answer 4

Post the options please, if you have any ????

Answer 5

Sure! One sec

Answer 6

B.) 3n(n+1) over 2, C. n(n+1) over 2 D. n(n+1) E. 5(n(n+1)divided by 2

Answer 7

I'll try to rephrase the choices..

Answer 8

k

Answer 9

It might be better to write each choice.

Answer 10

no. it's ok.

Answer 11

whts A?

Answer 12

n(n+1)/2 (the entire equation is divided by 2.)

Answer 13

god. wht math u in?

Answer 14

i keep getting just 25.

Answer 15

I'm taking PLATO for Algebra 1. It really sucks.. I'm a senior and if I don't pass these questions, I don't graduate >.>

Answer 16

@AccessDenied

Answer 17

good luck;)

Answer 18

A. and C. are the same? (n (n+1)) over 2
I tried this a few times and did not get an answer from those answer choices. Could you rewrite and make sure?

Answer 19

A and C are the same EXCEPT that,at the end of the equation for C,there is a '+ n'

Answer 20

So it would be (n((n+1)) over 2, and 'n' is added to the entire equation.

Answer 21

You gave the sequence: 3,4,5,6,7...
Your first term is 3.
We can find the general kth term by induction, the common difference being 1
1st term: 3 = 3 + 0*1
2nd term: 4 = 3 + 1*1
3rd term: 5 = 3 + 2*1
kth term: = 3 + (k-1) *1 = 2 + k

The last term is the nth term, so k=n; 2 + n.
That means we can use our formula: S = (a_1 + a_n) * #terms / 2 = (3 + (2+n)) * n/2
But I didn't see one of the answer choices match this...

Answer 22

Sorry for the confusion :/

Answer 23

No worries. Did you at least get the answer or was it not an answer choice to begin with?

Answer 24

I guessed. It wasn't the right thing to do, but whatever. It was too hard phrasing the answers. Thanks for your help,though.