Question

if 4, 12, 20, and so on are in AP then the sum of the first 20 terms is​

Answer 1

Hiii

Good morning

4,12,20,.......,20terms

a = 4

d= 12 - 4
d= 8
n = 20

S(n) = n/2 [ 2a+ (n - 1) d]

S(20) = 20/ 2 [ 2(4) + (20 - 1) 8]

S(20)= 10[ 8 + (19)8]

S(20) = 10 [ 8 + 152]

S(20)= 10[160]

S(20) = 1600

May it is helpful for you.

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Answer 2

Answer:

Step-by-step explanation:

4+12+20+28........20th terms

S=n/2[2a+(n-1)d] put the value in this

Where

D diff between digits 8

A first digit 4

N no of digits 20