Question

given a = 2, d=8, S = 90, find n and a
n​

Answer 1

Answer:

$s = n \div 2(a + (n - 1)d)$

Step-by-step explanation:

90 = n/2 { 2 + (n-1) 8}

180 = n ( 2 + 8n - 8 )

180 = n ( 8n - 6 )

180 = 8n² - 6n

4n²- 3n - 90 = 0

from here find value of n

then

we know that

$an \: = 2a + (n - 1)d$

put values of a , n & d

you will get your ans

Answer 2

This is my answer...

I hope it will be help you.