Find the sum of 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 = 2 - 3n.

Given, nth term, an = 2 – 3nPut n = 1, a1 = 2 – 3(1) = -1Put n = 25, a15= 2 – 3(15) = -43Therefore, S25 = (-1 – 43)= (-44) = -925

Q26 of 202 Page 9

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

Given, n^th term, a_n = 2 – 3n

Put n = 1, a₁ = 2 – 3(1) = -1

Put n = 25, a₁₅= 2 – 3(15) = -43

Therefore, S₂₅ = (-1 – 43)

= (-44) = -925

Find the sum of the first 15 terms of each of the following sequences having n^th term as

(i)

(ii)

(iii)

(iv)

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

Find the sum of the 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.