Question

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Answer 1

\[\sum_{n=1}^{14}(3n+2)\]this?

Answer 2

Can you find the sigma thing in the equation editor?

Answer 3

I'll type the hint to the solution while you are practicing.

Answer 4

\[S_n=\color{red}{\frac{1}{2}(a_1+a_n)}n\]

Answer 5

this is the sum for n terms in an arithmetic sequence.
Can you find 2 things for me, based on your sigma notation:
\[\sum_{n=1}^{14}(3n+2)\] this is the sigma,
and you need to tell me:
\[1)~~a_1\]\[2)~~a_{14}\]

Answer 6

hey? you left, and I was trying to help you!

Answer 7

Oh, okay, apologize

Answer 8

find what I asked for me please.

Answer 9

yes, so when you plug in 1 for n, you get a1, and when you plug in 14 for n, you get a14.
(you are plugging into "3n+2")

Answer 10

what are a1 and a14, can you tell me?

Answer 11

If I wanted to find a2, I would plug in 2 for n into 3n+2.
So,
a2= 3(2)+2
a2=5+2
a2=7

can you similarly find a1, and a14?

Answer 12

I am still here

Answer 13

a1 is 5 that is correct.
a(14) is not 19.

Answer 14

If, a(n) = 3n+2
then, a(14)=3(14)+2

correct?

Answer 15

so a(14)+?

Answer 16

I meant, so a(14)=?

Answer 17

a(14) = 3(14)+2
a(14) = 42+2
a(14) = 44

Answer 18

good?

Answer 19

3(14) means 3 times 14, just like 3n means 3 times n.

Answer 20

yes:)

Answer 21

\[\large S_{14}=~14 \times \frac{1}{2} \times (a_{{_1}}+a_{_{14}})\]

Answer 22

plug in the a1 and a14 that you found, and solve for S14.

Answer 23

tell me what you get after you are done.

Answer 24

http://www.wolframalpha.com/input/?i=14+times+1%2F2+times+%285%2B44%29

Answer 25

see how I am plugging it in there?

Answer 26

good luck.