how many terms of the AP:9,17,25,...must be taken to give a sum ofb636
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Answer:
12 terms
Step-by-step explanation:
The question is very easy.
In the A.P given
9, 17, 25,........
a= 9. d= 17-9= 8
Sn= 636 ...(given)
Sn= n/2 {2a+(n-1).d}
636 = n/2 {18 + (n-1)×8}
636×2 = n(18+8n-8)
636×2 = 8n² + 10n
1272 = 8n² + 10n
8n² + 10n - 1272 = 0
4n² + 5n - 636 = 0
solving above equation you get
n=12 and n = -53/4
As no. of terms are never negative .
Therefore 12 TERMS OF A.P ARE REQUIRED TO GET THE SUM OF
636
If you think I was right, Surely mark it as brainliest !!!
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