FIND THE SUM OF THE FIRST 15 TERMS OF AN AP,WHOSE nth term is (4n +1).
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here nth term is 4n+1
so a₁=4x1 + 1=5
as n=15
so, l=4x15 +1=61
and we know Sₓ=x/2[a+l]
so here S₁₅=15\2 (15+61)
⇒S₁₅=15/2(76)=570
so a₁=4x1 + 1=5
as n=15
so, l=4x15 +1=61
and we know Sₓ=x/2[a+l]
so here S₁₅=15\2 (15+61)
⇒S₁₅=15/2(76)=570
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