{
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  "question_id": "q-20261014-advance-20261109-r05-binomial-theorem-0006",
  "pilot_number": "P1000-0406",
  "number": 406,
  "family_id": "qf-mod40-binomial-coefficient",
  "title": {
    "zh-Hant": "第 406 題：二項式定理",
    "en": "Question 406: Exact Binomial Coefficients Keep k and n Minus k Distinct"
  },
  "original_question": {
    "schema_version": "ocme-question-v0.1",
    "id": "q-20261014-advance-20261109-r05-binomial-theorem-0006",
    "batch_id": "batch-20261014-advance-20261109-r05-binomial-theorem-foundations",
    "language": "zh-Hant",
    "source_mko_ids": [
      "mko-binomial-theorem"
    ],
    "title_zh": "二項式定理",
    "stem_zh": "commutative coefficient setting與n in natural including zero。操作=binomial-coefficient；資料={\"n\":5,\"k\":5}。請依 exact_ordered_tuple_declared_by_interface 欄序回答。",
    "answer": {
      "kind": "expression",
      "value": "(5, 5, 1, 1, 是)",
      "explanation_zh": "Wave6第三層核對=(5, 5, 1, 1, 是)；依完整明示資料獨立重算；coefficients exact且k、n-k exponents不可錯置；n=0給constant one；不套用negative/noninteger exponent或noncommuting variables；combinatorial witness選k個y factors。"
    },
    "difficulty": {
      "band": "undergraduate_core",
      "level": 1,
      "skills": [
        "二項式定理"
      ]
    },
    "variant": {
      "family_id": "qf-mod40-binomial-coefficient",
      "seed": 202611095006,
      "parameters": {
        "n": 5,
        "k": 5,
        "domain": "Exact_commutative_binomial_theorem",
        "operation": "binomial-coefficient",
        "semantic_template": "qf-mod40-binomial-coefficient/{\"k\":5,\"n\":5}"
      }
    },
    "verification": {
      "status": "candidate",
      "checks": [
        "producer_exact_finite_or_symbolic_model",
        "producer_source_snapshot_check",
        "producer_substantive_template_deduplication",
        "producer_json_schema"
      ],
      "warning_zh": "候選須主端重算；不構成人工審定、single-element stabilizer、finite-prefix BW、single-cover compactness、zero-mass division、noncommutative binomial、incomplete Möbius factorization、bounded-search nonmembership、Lean或Evidence。"
    },
    "provenance": {
      "generator_role": "question_producer",
      "generator_model": "model_unknown",
      "generated_at": "2026-10-14",
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  },
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    "schema_version": "ocme-question-localization-v0.1",
    "question_id": "q-20261014-advance-20261109-r05-binomial-theorem-0006",
    "batch_id": "batch-20261014-advance-20261109-r05-binomial-theorem-foundations",
    "locale": "en",
    "translation_state": "ai_candidate",
    "source": {
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      "family_id": "qf-mod40-binomial-coefficient",
      "seed": 202611095006,
      "semantic_template": "qf-mod40-binomial-coefficient/{\"k\":5,\"n\":5}"
    },
    "fields": {
      "title": "Exact Binomial Coefficients Keep k and n Minus k Distinct",
      "stem": "Use integer n=5 with 0≤n≤50 and integer k=5 with 0≤k≤n. The coefficient setting has commutative multiplication. Give (n, k, coefficient, symmetric_coefficient, equal).",
      "answer": {
        "kind": "expression",
        "value": "(5, 5, 1, 1, Yes)",
        "explanation": "Compute exact C(n,k) and C(n,n−k) and their equality. These count choices of k y-factors from n factors, including both endpoints and n=0. The exact result, retaining the requested order, is (5, 5, 1, 1, Yes)."
      },
      "skills": [
        "Exact Binomial Coefficients Keep k and n Minus k Distinct"
      ],
      "verification_warning": "This is a candidate exercise. Mechanical recomputation checks only the stated conditions and this instance; it is neither a formal proof nor human review."
    }
  },
  "givens": [
    {
      "id": "G001",
      "text": {
        "zh-Hant": "commutative coefficient setting與n in natural including zero。操作=binomial-coefficient；資料={\"n\":5,\"k\":5}。請依 exact_ordered_tuple_declared_by_interface 欄序回答。",
        "en": "Use integer n=5 with 0≤n≤50 and integer k=5 with 0≤k≤n. The coefficient setting has commutative multiplication. Give (n, k, coefficient, symmetric_coefficient, equal)."
      }
    }
  ],
  "steps": [
    {
      "id": "S001",
      "uses": [
        "G001"
      ],
      "before": "n=5≥0; multiplication commutes",
      "after": "group the finite product by the number of y choices",
      "relation": "implies",
      "rule_id": "commutative_product",
      "conditions": [],
      "explanation": {
        "zh-Hant": "每個因子選x或y，依選y的次數分組，係數先作整數計數。",
        "en": "Choose x or y in each factor and group by the number of y choices; count coefficients as integers first."
      },
      "reverse_audit": {
        "kind": "premise_and_result_audit",
        "explanation": {
          "zh-Hant": "係數先在整數中計數；不在一般係數環中除以可能不可逆的階乘。",
          "en": "Count coefficients in the integers first; do not invert possibly nonunit factorials in a general coefficient ring."
        }
      },
      "arithmetic": null
    },
    {
      "id": "S002",
      "uses": [
        "G001",
        "S001"
      ],
      "before": "choose 5 positions out of 5",
      "after": "C(5,5)=120/(120·1)=1",
      "relation": "implies",
      "rule_id": "subset_count",
      "conditions": [],
      "explanation": {
        "zh-Hant": "選取 k 個位置的每個子集只計一次；除掉兩組內部排列後得到整數係數。",
        "en": "Count each k-position subset once, dividing out reorderings inside each of the two groups."
      },
      "reverse_audit": {
        "kind": "premise_and_result_audit",
        "explanation": {
          "zh-Hant": "係數先在整數中計數；不在一般係數環中除以可能不可逆的階乘。",
          "en": "Count coefficients in the integers first; do not invert possibly nonunit factorials in a general coefficient ring."
        }
      },
      "arithmetic": {
        "operation": "binomial_count",
        "inputs": [
          "5",
          "5"
        ],
        "output": "1",
        "label": "C(5,5)"
      }
    },
    {
      "id": "S003",
      "uses": [
        "G001",
        "S002"
      ],
      "before": "choose 0 positions out of 5",
      "after": "C(5,0)=120/(1·120)=1",
      "relation": "implies",
      "rule_id": "subset_count",
      "conditions": [],
      "explanation": {
        "zh-Hant": "選取 k 個位置的每個子集只計一次；除掉兩組內部排列後得到整數係數。",
        "en": "Count each k-position subset once, dividing out reorderings inside each of the two groups."
      },
      "reverse_audit": {
        "kind": "premise_and_result_audit",
        "explanation": {
          "zh-Hant": "係數先在整數中計數；不在一般係數環中除以可能不可逆的階乘。",
          "en": "Count coefficients in the integers first; do not invert possibly nonunit factorials in a general coefficient ring."
        }
      },
      "arithmetic": {
        "operation": "binomial_count",
        "inputs": [
          "5",
          "0"
        ],
        "output": "1",
        "label": "C(5,0)"
      }
    },
    {
      "id": "S004",
      "uses": [
        "G001",
        "S003"
      ],
      "before": "choose subset of size 5",
      "after": "its complement has size 0",
      "relation": "implies",
      "rule_id": "subset_complement_bijection",
      "conditions": [],
      "explanation": {
        "zh-Hant": "取補集是互逆映射，因此這兩個選法數目相同。",
        "en": "Taking complements is an invertible map, so the two counts agree."
      },
      "reverse_audit": {
        "kind": "premise_and_result_audit",
        "explanation": {
          "zh-Hant": "係數先在整數中計數；不在一般係數環中除以可能不可逆的階乘。",
          "en": "Count coefficients in the integers first; do not invert possibly nonunit factorials in a general coefficient ring."
        }
      },
      "arithmetic": null
    },
    {
      "id": "S005",
      "uses": [
        "G001",
        "S004"
      ],
      "before": "C(5,5)=1; C(5,0)=1",
      "after": "symmetric coefficients equal: 是",
      "relation": "implies",
      "rule_id": "coefficient_symmetry",
      "conditions": [],
      "explanation": {
        "zh-Hant": "數值核對符合補集雙射；n=0仍只有空子集一種。",
        "en": "The values agree with the complement bijection; n=0 still has exactly the empty subset."
      },
      "reverse_audit": {
        "kind": "premise_and_result_audit",
        "explanation": {
          "zh-Hant": "係數先在整數中計數；不在一般係數環中除以可能不可逆的階乘。",
          "en": "Count coefficients in the integers first; do not invert possibly nonunit factorials in a general coefficient ring."
        }
      },
      "arithmetic": null
    }
  ],
  "math_model": {
    "result": [
      5,
      5,
      1,
      1,
      true
    ]
  },
  "conclusion": {
    "canonical_value": "(5, 5, 1, 1, 是)",
    "explanation": {
      "zh-Hant": "上述完整代值與條件核對得到原題答案；欄位次序及真假標記保持原始合約。",
      "en": "The full substitutions and premise audits recover the original answer, retaining its field order and verdict meanings."
    }
  },
  "definition_note": {
    "zh-Hant": "0≤k≤n 的整數計數；C(n,k) 為選 k 個位置的子集數，補集雙射給出對稱性。",
    "en": "Integer counting with 0≤k≤n. C(n,k) counts k-position subsets; the complement bijection gives symmetry."
  },
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      "en": "Source-bound pedagogical derivation candidate: exact arithmetic and finite enumeration are not independent AI review or general formal proof. Original questions, answers, MKOs, formulas, ASTs and history remain unchanged."
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