Question

Prove that : Sn= u + a/2(2n-1)​

Answer 1

Explanation:

Sn=Sn-S(n-1)

=(un+1/2an^2) - {u(n-1)+1/2a(n-1)^2}

=un+1/2an^2 - un+u - 1/2an^2-1/2a+an

=u + an - 1/2a

=u + 1/2a(2n-1)

Answer 2

Answer:

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Explanation:

u+1/2a(2n-1)