Question

how many terms of the series -9,-6,-3......must be taken so that the sum of them is 66

Answer 1

Step-by-step explanation:

a = t1 = -9

t2 = -6

d = t2 -t1 = -9-(-6) = -3

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

66 = n/2 [-18 -3n +3]

132 = n [ -3n -15]

132 = -3n^2 -15n

3n^2 +15n +132 = 0

n = 27

so sum of 27 th terms is 66

Answer 2

Answer: -9-6-3+3+6+9+12+15+18+21

Step-by-step explanation: