Find the series in A.P whose sum to n terms is n*(n+2)
1 answer:
Answer:
3, 5, 7, 9, 11, .........
Step-by-step explanation:
Given
= n(n + 2) , then
S₁ = 1(1 + 2) = 1(3) = 3 ⇒ a₁ = 3
S₂ = 2(2 + 2) = 2(4) = 8
S₃ = 3(3 + 2) = 3(5) = 15
Thus
a₂ = S₂ - S₁ = 8 - 3 = 5
a₃ = S₃ - S₂ = 15 - 8 = 7
The first 3 terms are 3, 5, 7
This is an AP with common difference d = 2, then
a₄ = a₃ + 2 = 7 + 2 = 9
a₅ = a₄ + 2 = 9 + 2 = 11
and so on
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