Question

(Answered myself, I did this for others gain since it wasn't on this site)

Answer 1

Answer

Given series,

12 + 18 + 24 + 30 + . . . + 198

first term of series, a = 12

common difference,d = 18- 12 = 6

Last term of the series, a_n or l = 198.

a) The expression of arithmetic sequence given by the explicit rule is

    $a_n = a + (n-1)d$

    $a_n = 12 + (n-1)6$

b) number of terms in the series

    $198 = 12 + (n-1)6$

   $n-1 = 31$

   $n = 32$

c) value of the series

   $S_n = \dfrac{n}{2}(a+l)$

   $S_n = \dfrac{32}{2}(12+198)$

  $S_n = 3360$

Answer 2

Answer:

1.)  an= 12 + (n-1) 6

2.) n = 32

3.) C. 3,360

Step-by-step explanation: