Sum of the squares of first n natural numbers exceeds their sum by 330, then n =
Question
Sum of the squares of first n natural numbers exceeds their sum by 330, then n =
Solution
The sum of the squares of the first n natural numbers is given by the formula n(n+1)(2n+1)/6.
The sum of the first n natural numbers is given by the formula n(n+1)/2.
According to the problem, the sum of the squares of the first n natural numbers exceeds their sum by 330. So, we can set up the following equation:
n(n+1)(2n+1)/6 - n(n+1)/2 = 330
Solving this equation will give us the value of n.
First, simplify the equation:
n(n+1)[(2n+1)/6 - 1/2] = 330
This simplifies to:
n(n+1)(n-2)/6 = 330
Multiply both sides by 6 to get rid of the fraction:
n(n+1)(n-2) = 1980
This is a cubic equation, and solving it is a bit tricky. But we can guess and check to find that n=10 is a solution.
So, n = 10.
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