Question

1) Given a1 = 8 , an = 62 , Sn = 210 ;

find d and n .

2) Derive the formula of r in terms of a1 , an , and n.

Answer 1

answer

sn=n/2(2a+n-1)d)

210=n/2(16+(n-1)d)0

420=n(16+(n-1)d)