Question

if an =n²+1 then s2 I will be
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Answer 1

Step-by-step explanation:

An = n² + 1

A(1) = a = 1² + 1 = 1 + 1 = 2

A(2) = 2² + 1 = 4 + 1 = 5

d = 5 - 2 = 3

Now ,

S(2) = 2/2 { 2(2) + (2-1)3 }

= 1 { 4 + 3 }

= 1 × 7

= 7