Question

The sum of the first 30 terms of the sequence an = 6n + 5 is _____.

Answer 1

i know there is a snap way to do this, but i don't know what it is. i would remember that
\[\sum_{k=1}^n k =\frac{n(n-1)}{2}\] and do the following

Answer 2

a1=11
d=6
n=30

Answer 3

arithmetic progression

Answer 4

\[\sum_{k=1}^{30} 6k+5=6\times \sum_{k=1}^{30}k+5\times \sum_{k=1}^{30}1\]

Answer 5

get
\[6\times \frac{30\times 31}{2}+5\times 30\]

Answer 6

A_clan might have a snappier way

Answer 7

i get 2940

Answer 8

\[\frac{n}{2}(first + last)\]

Answer 9

30(6(1) + 5 + 6(30) + 5)
----------------------
2

15(6 + 5 + 180 + 5)

15(16 + 180)

15(176) = 2640 is my guess

Answer 10

to add the numbers 1 to 9

9(1+9)
------ = 90/2 = 45
2

n(first + last)
----------- gets you the sum
2

Answer 11

lets dbl chk that

4+9+16 = 29

3(4+16)
-------- = 3(20)/2 = 60/2 = 30
2

ack! well its close :)