What is the arithmetic sequence formula?

Answer 1

the formula is:

Sn= n [2(A1)+(n - 1)d]

2

for example the given sequence is when A1 = 4 and n = 10 when d = 2 here is the solution:

Sn = 4 [2(4)+(10 - 1)2]

2

Sn= 2 [6+(9)(2)

Sn = 2 [6+18]

Sn = 2 (24)

Sn = 48

see?