Question

7. The sum of first n terms of an AP is (5n - n?). The nth term of the AP is
(a) (5-2n) (b) (6-2n) (c) (2n-5) (d) (2n-6)​

Answer 1

Answer:

Given S

n

=2n

2

+5n

S

n−1

=2(n−1)

2

+5(n−1)

=2(n

2

−2n+1)+5n−5

=2n

2

−4n+2+5n−5

=2n

2

+n−3

Now, t

n

=S

n

−S

n−1

=2n

2

+5n−(2n

2

+n−3)

=2n

2

+5n−2n

2

−n+3

=4n+3

Step-by-step explanation:

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Answer 2

$\small\bold{\underline{\sf{\blue{solution:-}}}}$

d =a2-a1

=3

If all term satisfies here and common difference is 3 it is an ap.

So,this is an AP

First term=8