Math Problem Statement

Fill in each blank below with a positive integer to make the following statement true for every positive integer n: (binomial coefficient formula image)

Solution

The equation provided is a combinatorial identity involving binomial coefficients. The goal is to fill in the blanks to make the equation true for every positive integer nn.

The given equation can be written as:

(n2)=(blank)(n(blank))+(blank)(n(blank)).\binom{n}{2} = \text{(blank)} \cdot \binom{n}{\text{(blank)}} + \text{(blank)} \cdot \binom{n}{\text{(blank)}}.

We need to identify the appropriate integers for the blanks.

Step-by-step explanation:

  1. The left-hand side, (n2)\binom{n}{2}, represents the number of ways to choose 2 objects from nn objects.

  2. The right-hand side should decompose (n2)\binom{n}{2} into a weighted sum of two binomial coefficients.

  3. A standard decomposition for (n2)\binom{n}{2} is: (n2)=1(n1)+1(n0).\binom{n}{2} = 1 \cdot \binom{n}{1} + 1 \cdot \binom{n}{0}.

    Explanation:

    • (n1)\binom{n}{1} counts the ways to select 1 object, multiplied by a coefficient of 1.
    • (n0)\binom{n}{0} counts the ways to select no objects (always equal to 1), multiplied by a coefficient of 1.
  4. Substituting into the blanks, the complete equation becomes: (n2)=1(n1)+1(n0).\binom{n}{2} = 1 \cdot \binom{n}{1} + 1 \cdot \binom{n}{0}.

Final Answer:

The blanks should be filled as:

  • First blank: 11,
  • Second blank: 11,
  • Third blank: 11,
  • Fourth blank: 00.

Let me know if you need further details or explanations!


Here are 5 related questions to expand your understanding:

  1. What is the formula for the binomial coefficient (nk)\binom{n}{k}, and how is it derived?
  2. Can you explain why (n0)=1\binom{n}{0} = 1 for any positive integer nn?
  3. How does this identity relate to Pascal’s triangle?
  4. Can this identity be extended to cases where we decompose (n3)\binom{n}{3}?
  5. What is the combinatorial interpretation of multiplying a binomial coefficient by a scalar?

Tip: Understanding binomial coefficients often involves recognizing their relationship with combinations and Pascal’s triangle. This can help in visualizing and verifying identities!

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Math Problem Analysis

Mathematical Concepts

Combinatorics
Binomial Coefficients
Combinatorial Identities

Formulas

Binomial coefficient formula: \( \binom{n}{k} = \frac{n!}{k!(n-k)!} \)
Combinatorial identity: \( \binom{n}{2} = 1 \cdot \binom{n}{1} + 1 \cdot \binom{n}{0} \)

Theorems

Pascal's Identity
Basic properties of binomial coefficients

Suitable Grade Level

Grades 10-12