The expression $(x + y)^n$ represents the expansion of a binomial raised to a power, known as the binomial theorem. This theorem provides a way to expand expressions of this form into a sum involving terms of the form $C(n, k) x^{n-k} y^k$, where $C(n, k)$ is the binomial coefficient that counts the number of ways to choose $k$ elements from $n$ elements. Understanding this expansion is essential in combinatorics, algebra, and probability theory, allowing for various applications in these fields.
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