If sum of first n terms of a sequence is 4n^2 +5n then the general term of sequence is
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I've considered the sequence to be A.P as it wasn't mentioned
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we know Sn=n/2(2a+(n-1)d)
so according to the question
s1=4×1^2+5×1=9
s2=4×2^2+5×2=26
s1 will be the first term of the AP
and S2-S1 will be the second term.
so a1=9
a2=17
and d=a2-a1=8
we know that the general formula of an AP is a+(n-1)d
so we will substitue the value of a and d in it which Will give:
9+8n-8
=8n+1
so the general formula is 8n+1
so according to the question
s1=4×1^2+5×1=9
s2=4×2^2+5×2=26
s1 will be the first term of the AP
and S2-S1 will be the second term.
so a1=9
a2=17
and d=a2-a1=8
we know that the general formula of an AP is a+(n-1)d
so we will substitue the value of a and d in it which Will give:
9+8n-8
=8n+1
so the general formula is 8n+1
ankit722:
i hope it helped u
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