Question

(4) For an AP is Sn= 5n2-3n, then an=​

Answer 1

Answer:

Let an be the nth term of the A.P.

Then, an =Sn −Sn−1

⟹a n =(5n 2+3n)−{5(n−1) 2 +3(n−1)}

.......... [Replacingnby(n−1)inSn

to get Sn−1=5(n−1) 2 +3(n−1)]

⟹an=(5n 2+3n)−(5n 2−7n+2)

⟹an =10n−2