Problem : Define the arithmetic sequence a _n = 4n - 3 recursively.

Problem : Define the arithmetic sequence a ₁ = 6 ; a _n+1 = a _n - 2 explicitly.

Problem : What is the sum of the first six terms of the sequence a _n = 2n + 6 ?

Solution for Problem 3 >>

S ₆ = (a ₁ + a ₆) = 3(8 + 18) = 78 .

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Problem : What is the sum of the first 45 terms in the arithmetic sequence a ₁ = 3 ; a _n+1 = a _n + 5 ?

Solution for Problem 4 >>

S ₄5 = 45a ₁ + (45d - d )= 135 + (22.5)(220) = 5085 .

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