Question

2. The first term of an arithmetic sequence is 1 and the
sum of the first four terms is 100. Find the first four
terms​

Answer 1

Step-by-step explanation:

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

we have

S(n) = 100 , a = 1 , n = 4

then,

A.T.Q.,

100 = 4/2 [ 1 + (4-1)d]

100/2 = 1 + 3d

3d = 50-1

d = 49/3

then other terms are

a2 = 1 + 49/3 = 52/3

a3 = 52/3 + 49/3 = 101/3

a4 = 101/3 + 49/3 = 150/3