Question

find the sum of each arithmetic sequence with the given condition​

Answer 1

Step-by-step explanation:

given that _

a1 = 3 An = 99 d = 3

a to q _

an = a +(n-1) d

99 = 3+ nd- d

99 = 3 + n× 3 - 3

99-3 + 3= 3n

102-3= 3n

99 = 3n

n= 11

then we find the sn of Ap , l = an

sn = n/2 ( a+l)

sn = 11 /2 ( 3+99)

sn = 11/2 × 102

sn= 11 × 51 = 561 ans.