Question

The sum of first 18 terms of an ap whose n term is 3 - 2 n is

Answer 1

Answer:

Given nth term of AP an = 3 - 2n Put n = 1, we get a1 = 3 - 2 = 1 Put n = 2, we get a2 = 3 - 4 = - 1 Hence d = -1 - 1 = -2 a15 = 3- 30 = - 27 Sum of 15 terms = (15/2)[1 + (-27)] = (15/2) × - 26 = -195

Step-by-step explanation:

Answer. Given nth term of AP an = 3 - 2n Put n = 1, we get a1 = 3 - 2 = 1 Put n = 2, we get a2 = 3 - 4 = - 1 Hence d = -1 - 1 = -2 a15 = 3- 30 = - 27 Sum of 15 terms = (15/2)[1 + (-27)] = (15/2) × - 26 = -195