15. If the sum of first n terms of a series in A.P. is n^2+3n, find the 10thterm.
b) 16
a) 10
c) 18
d) 22
Answers
Answered by
5
Answer:-
The Answer Is Option d) 22.
Explanation:-
Given:-
- Sum of first n terms of an AP is n² + 3n.
To Find:-
- The 10th term of the AP.
Formula Used:-
Where,
- Term.
- = Sum of n terms.
Therefore,
Also,
And Hence,
Similarly,
Therefore,
Therefore 10th term is 22.
So The Final Answer is Option (d).
Answered by
2
Given ,
The sum of first n terms of a series in AP is (n)² + 3n
As we know that ,
And
Thus ,
First term = (1)² + 3(1) = 4
Second term = 4 - (2)² + 3(2) = 6
∴Common difference (d) = 2
Now , the nth term of an AP is given by
Thus ,
10th term = 4 + (10 - 1)2
10th term = 4 + 18
10th term = 22
∴ The 10th term of given AP is 22
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