Find a formula for the sum of the first n natural numbers. Assume that the formulais a quadratic polynomial in n.
Question
Find a formula for the sum of the first n natural numbers.
Assume that the formula is a quadratic polynomial in n.
Solution
The formula for the sum of the first n natural numbers is given by the formula:
S = n/2 * (n + 1)
Here's how we derive it:
- Let's denote the sum of the first n natural numbers as S. So, S = 1 + 2 + 3 + ... + n.
- Now, let's write this sum backwards, i.e., S = n + (n-1) + (n-2) + ... + 1.
- If we add these two equations, we get 2S = (n+1) + (n+1) + ... + (n+1) (n times). So, 2S = n*(n+1).
- Therefore, S = n/2 * (n + 1).
This formula is a quadratic polynomial in n, as required.
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