Question

In an A.P the sum of its first n terms is 6n-n^2 .find its 25th term

Answer 1

Answer :

$\bf S_n = 6n - n^{2} \\ \\ \bf S_{25} = 6 \times 25 - (25) ^ {2} \\ \\ \bf S_{25} = 150 - 625 \\ \\ \red{\bf S_{25} = - 475}$

Answer 2

Answer:

Step-by-step explanation:

Sn = 6n-n²

S1 = 6×1-(1)¹

=6-1=5

S2 = 6×2-(2)²

=12-4=8

S3 = 6×3-(3)²

=18-9=9

Ap formed = 5,8-5=3, 9-8=1

=5,3,1....

A=5 , d=3-5=-2

An= a+(n-1)d

=5+(25-1)(-2)

=5+(24)(-2)

=5-48 = -43

Hope it works

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