Math, asked by rajvisavadia2005, 6 months ago

How many terms of the AP -17,-15,-13,...........are needed to make the sum -72?

Answers

Answered by shweta7289
1

Step-by-step explanation:

let this is the sum of n terms

d=a2 -a1 = -15 - (-17)= -15+17 =2

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

-72 = n (-34+ ( n-1)2)/2

-144 =-34n +2n^2- 2n

-72 =n^2-18n

n^2 -18n+72=0

(n-12) (n-6)=0

n=12 or 6

double answer means that sum of 7th term to 12th term is 0.

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