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Exercise 1537Combinatorics › Binomial coefficientsL1Added 3 Nov 2026

Generating function of binomial row

#generating function#binomial row#polynomial

Statement

Show that ∑k=0n(nk)xk=(1+x)n\sum_{k=0}^{n}\binom{n}{k}x^k=(1+x)^n.

Hint

Binomial theorem.

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Solution

Binomial theorem. (1+x)n=∑k(nk)xk(1+x)^n=\sum_k\binom{n}{k}x^k.

Interpretation. The row of Pascal's triangle gives the coefficients of the polynomial (1+x)n(1+x)^n.

Conclusion. The generating function of the nn-th row is (1+x)n(1+x)^n.