The sum of first n term os an AP is given by Sn=3n^2+2n. Determine the AP and its 15th term
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the answer that I solved is using substitution method
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LuvNoor111:
the coming answer is 5,11,17,____,89
I dont think it would be so big .. are you telling about the sum of 15 numbers in AP ??
yes
okay my answer was for the 15th term in AP
Answered by
26
Here is your solution
Given as
sn=3n^2+2n
To find out we need to find first term and Common difference
Let n= 1
We got the first term a = 5
Now also put n=2
Since it's the sum of 2 term =16
2nd term = S2 - a
= 16- 5
= 11
Now we have
a1 = 5 and a2 = 11
Now d = a2- a1
d = 11- 5 = 6
Now 16th term
15th term =a+14d=5+14(6)=89
hope it helps you
Given as
sn=3n^2+2n
To find out we need to find first term and Common difference
Let n= 1
We got the first term a = 5
Now also put n=2
Since it's the sum of 2 term =16
2nd term = S2 - a
= 16- 5
= 11
Now we have
a1 = 5 and a2 = 11
Now d = a2- a1
d = 11- 5 = 6
Now 16th term
15th term =a+14d=5+14(6)=89
hope it helps you
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