Find the sum of the first 25 terms of an A.P. whose n th term is given by . The image displays the formula for the nth term of an arithmetic progression as a_n = 7 - 3n.

Given, an= 7 - 3nPut n = 1a1= 7 – 3(1) = 4Put n = 25a25= 7 – 3(25) = -68 = lS25= [4 – 68]= 25 [-32] = -800

Q27 of 202 Page 9

Find the sum of the first 25 terms of an A.P. whose n^th term is given by .

Given, a_n= 7 - 3n

Put n = 1

a₁= 7 – 3(1) = 4

Put n = 25

a₂₅= 7 – 3(25) = -68 = l

S₂₅= [4 – 68]

= 25 [-32] = -800

Find the sum of first 20 terms of these sequence whose n^th term is .

Find the sum of first 25 terms of an A.P. whose n^th term is given by .

Find the sum of the first 25 terms of an A.P. whose second and third terms are 14 and 18 respectively.

If the sum of 7 terms of an A.P. is 49 and that of 17 term is 289, find the sum of n terms.