Question

nth term of an ap is4n_1find sum of first18 terms​

Answer 1

first find the number of terms by using this formula

a r^ n-1

than after finding n

use sum formula

Answer 2

Answer:

Step-by-step explanation:

$A_n$ = 4n - 1

⇒ $A_{1}$ = 4 - 1 = 3

⇒ $A_{18}$ = 4(18) - 1 = 71

$S_{n}$ = n/2( a + l )

$S_{18}$ = 18/2 ( 3 + 71 )

     = 9(74)    

     = 666