how many terms of the AP 9, 17, 25 must be taken to get sum of 636
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here a-9 d-8 Sn-636
Sn=n/2×(2a+(n-1)d)
636=n/2 (18+(n-1)8)
636=n/2×10+8n
n=12.
Sn=n/2×(2a+(n-1)d)
636=n/2 (18+(n-1)8)
636=n/2×10+8n
n=12.
dimpy6:
can u briefly explain the second last step
and how u got it as 12
when u will solve second last step further you will get 4n×n+5n -636.After factorising u will get ans n=2or n=-53/4
n=-53/4 doesn't satisfy conditions that's why ans is n=12
I have solve in same way as moderator had solve.
thk u
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