Question

The nth term of a series is given to be 3+n/4, find the sum of 105 terms of this series

Answer 1

find the 1st term and 2nd term then u will get d and a1 then put it in sum formula . acc to me ans should be 1470 . and 1st term is 1 and d is 1/4

Answer 2

Answer:

Step-by-step explanation:Given series= 3+n/4

First, let n=1

a1=3+1/4=4/4=1

a1=1

Now let n=2

So a2=3+2/4=5/4

now d(difference)=a2-a1

Therefore, d=5/4-1

d=5-4/4

d=1/4

Now S105=105/2(2×1+(105-1)1/4)

S105=105/2(2+104×1/4)

S105=105/2(2+26)

S105=105/2(28)

S105=105×14

S105=1470