Question

Please help me. I will medal & fan!!!!!!!!** :)

If the nth term of a sequence is 2n + 4, what is the sum of the first n terms?

A.) n(n+1)+4n
B.) n(n+1)/2 +n
C.) n(2n+4)
D.) n(n+1)(2n+1) /6 + 2n(n+1)
E.) 2n(n+1)/n

Answer 1

the first term is:
\[{a_1} = 2 \times 1 + 4 = ...?\]

Answer 2

I would just plug that in?

Answer 3

the first term is given by replacing n with 1 into your formula

Answer 4

the requested sum S is given by the subsequent formula:
\[S = \frac{{{a_1} + {a_n}}}{2} \times n\]

Answer 5

what is a_1?

Answer 6

8?

Answer 7

hint:
\[\large {a_1} = 2 \times 1 + 4 = 2 + 4 = ...?\]

Answer 8

I'm just a numskull and don't understand any of this. I thank you for time and effort. I will just guess at this point... Thank you, though. :)

Answer 9

please wait

Answer 10

the first term is a1=6 right?

Answer 11

now we have to substitute so we can write:
\[\large \begin{gathered}
S = \frac{{{a_1} + {a_n}}}{2} \times n = \frac{{6 + 2n + 4}}{2} \times n = \frac{{10 + 2n}}{2} \times n = \hfill \\
\hfill \\
= \left( {5 + n} \right)n = 5n + {n^2} \hfill \\
\end{gathered} \]

Answer 12

now we have this:
\[\Large n\left( {n + 1} \right) + 4n = {n^2} + n + 4n = {n^2} + 5n\]

Answer 13

n(2n+4) ?

Answer 14

I think that it is:
n(n+1)+4n

Answer 15

no it's n(n+1)+4n ??

Answer 16

that's right!

Answer 17

yay!! thank you!!

Answer 18

:)