Find the sum of first n terms of the Arithmetic Progression if the nth term of AP is : a) 2n + 1 b) 5-6n c) 5 + 2n d) 6 - n
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Answer:
ThegivnesequenceofanA.Pwith
t
n
=5+6n,n∈N
∴Thefirstterm,t
1
=5+6(1)=11
andthelasttermisthethenthtermt
n
=5+6n
Now,
SumofntermofA.Pisgivnby
S
n
=
2
n
[t
1
+t
n
]
=
2
n
(11+5+6n)
=n(8+3n)
=3n
2
+8ThegivnesequenceofanA.Pwith
t
n
=5+6n,n∈N
∴Thefirstterm,t
1
=5+6(1)=11
andthelasttermisthethenthtermt
n
=5+6n
Now,
SumofntermofA.Pisgivnby
S
n
=
2
n
[t
1
+t
n
]
=
2
n
(11+5+6n)
=n(8+3n)
=3n
2
+8
Hence,theoptionBisthecorrectanswer.
Hence,theoptionBisthecorrectanswer.
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