Question

142?

Answer 1

@Vocaloid

Answer 2

the sum formula is a bit different than the series formula

Answer 3

don't I substitute 20 for n

Answer 4

so first calculate a20 (the 20th term of the series)

Answer 5

10

Answer 6

if an = 7n + 2 and n = 20 what is an?

Answer 7

22

Answer 8

7(20)+2 = ?

Answer 9

142

Answer 10

sorry lol been working 15hrs

Answer 11

good, what about a1?

Answer 12

(what is an when n = 1?)

Answer 13

a1

Answer 14

7n + 2 = what when n = 1?

Answer 15

9

Answer 16

good so we get

sum = 20(9+142)/2 = ?

Answer 17

1510

Answer 18

good so 1510 is the sum