Question

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

Answer 1

Answer:

First term (A ) = 65

Common Difference (D) = 60-65 = -5

Sn = 0

N/2 × [ 2A + ( N-1) × D ] = 0

N × [ 2 × 65 + ( N-1) × -5 ] = 0 × 2

N ( 130 -5N + 5 ) = 0

130 - 5N + 5 = 0/N

135 - 5N = 0

-5N = -135

N = -135/-5

N = 27

Hence,

27 terms must be added to get the sum 0.

Answer 2

Answer:

35

Step-by-step explanation:

given:

a=-9

d=3

s=66

s=n/2{2a+(n-1)d}

66 =n/2((n-1)3-9

 132 =3n(n-1-3)

 44=n(n-4)

n*n+4n-44=0

by solving it,we get

n=35