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Hey, I couldn't find the answer to this question "Summation of r^3 × ncr from 0 to n?" , Please help out by answering this question?
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Hey, I couldn't find the answer to this question "Summation of r^3 × n...
Understanding the Summation
The summation of r^3 × nCr from 0 to n represents a combinatorial identity involving binomial coefficients. Here, r is a constant, and nCr (or C(n, r)) is the binomial coefficient representing the number of ways to choose r elements from a set of n elements.
Expression of the Summation
The expression can be written as:
- S = Σ (r^3 × nCr), where the summation runs from r = 0 to n.
Using Binomial Theorem
The binomial theorem states that:
- (x + y)^n = Σ (nCr × x^r × y^(n-r))
By differentiating this theorem, we can find relationships involving powers of r.
Applying the Identity
For the case of r^3, we can derive:
- S = n(n-1)(n-2)(1 + 1)^n
- This comes from applying differentiation three times to (1 + x)^n.
Final Result
The final result for the summation is:
- S = n^2(n + 1) / 4
This formula effectively summarizes the contribution of r^3 multiplied by the binomial coefficient over the range from 0 to n.
Conclusion
In summary, the summation of r^3 × nCr from 0 to n can be computed using binomial identities and differentiation techniques. The result provides a powerful tool for combinatorial problems and is rooted in the fundamental principles of binomial expansions.
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