{
  "schema_version": "ocme-reviewed-question-reader-v1",
  "question_id": "q-20261013-advance-20261021-r05-bisection-method-0077",
  "pilot_number": "R0003-02077",
  "number": 2077,
  "family_id": "qf-app21-bisection-width-after-steps",
  "title": {
    "zh-Hant": "第 2077 題：有限二分bracket",
    "en": "Question 2077: Geometric Width after a Declared Number of Halvings"
  },
  "original_question": {
    "schema_version": "ocme-question-v0.1",
    "id": "q-20261013-advance-20261021-r05-bisection-method-0077",
    "batch_id": "batch-20261013-advance-20261021-r05-bisection-method-foundations",
    "language": "zh-Hant",
    "source_mko_ids": [
      "mko-bisection-method"
    ],
    "title_zh": "有限二分bracket",
    "stem_zh": "已提供的符號 bracket 資料。操作=bisection-width-after-steps；資料={\"left\":[-2,1],\"right\":[6,1],\"steps\":1}。請依 [left,right,steps,width] 欄序回答。",
    "answer": {
      "kind": "expression",
      "value": "(-2, 6, 1, 4)",
      "explanation_zh": "應用擴展核對=(-2, 6, 1, 4)；依完整明示資料重算；完整明示的有限／精確切片不是一般定理或人員判定；不由異號自行推出根存在；只核對有限更新與寬度。"
    },
    "difficulty": {
      "band": "undergraduate_core",
      "level": 1,
      "skills": [
        "有限二分bracket"
      ]
    },
    "variant": {
      "family_id": "qf-app21-bisection-width-after-steps",
      "seed": 202610215077,
      "parameters": {
        "left": [
          -2,
          1
        ],
        "right": [
          6,
          1
        ],
        "steps": 1,
        "domain": "Declared_sign_bracket_updates",
        "operation": "bisection-width-after-steps",
        "semantic_template": "qf-app21-bisection-width-after-steps/{\"left\":[-2,1],\"right\":[6,1],\"steps\":1}"
      }
    },
    "verification": {
      "status": "candidate",
      "checks": [
        "producer_exact_finite_model",
        "producer_source_snapshot_check",
        "producer_substantive_template_deduplication",
        "producer_json_schema"
      ],
      "warning_zh": "僅為產生端候選及自檢；主端須另驗，不構成人工審定、一般定理、真實學生診斷、經驗預測、Lean執行或形式Evidence。"
    },
    "provenance": {
      "generator_role": "question_producer",
      "generator_model": "model_unknown",
      "generated_at": "2026-10-13",
      "contract_version": "ocme-question-factory-v0.1"
    }
  },
  "original_english_edition": {
    "schema_version": "ocme-question-localization-v0.1",
    "question_id": "q-20261013-advance-20261021-r05-bisection-method-0077",
    "batch_id": "batch-20261013-advance-20261021-r05-bisection-method-foundations",
    "locale": "en",
    "translation_state": "ai_candidate",
    "source": {
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      "family_id": "qf-app21-bisection-width-after-steps",
      "seed": 202610215077,
      "semantic_template": "qf-app21-bisection-width-after-steps/{\"left\":[-2,1],\"right\":[6,1],\"steps\":1}"
    },
    "fields": {
      "title": "Geometric Width after a Declared Number of Halvings",
      "stem": "Use only the supplied exact rational endpoints and declared signs in {-1,0,1}. Normalize rational results to reduced fractions with positive denominators, omitting /1 for integers. Sign data and width-halving do not establish root existence or convergence to a root; a separate theorem and its hypotheses would be required. initial left=-2/1, right=6/1, halvings=1≥0. Give (left,right,halvings,(right−left)/2^halvings). This is the geometric width formula without an earlier zero-stop, not a function-value error.",
      "answer": {
        "kind": "expression",
        "value": "(-2, 6, 1, 4)",
        "explanation": "Divide the exact initial width by the specified power of 2. Interpreting it as a root-location bound separately requires a root in the bracket. This explicit finite/exact slice is neither a general theorem nor a judgment about a person. The exact result, retaining the requested order, is (-2, 6, 1, 4)."
      },
      "skills": [
        "Geometric Width after a Declared Number of Halvings"
      ],
      "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": "已提供的符號 bracket 資料。操作=bisection-width-after-steps；資料={\"left\":[-2,1],\"right\":[6,1],\"steps\":1}。請依 [left,right,steps,width] 欄序回答。",
        "en": "Use only the supplied exact rational endpoints and declared signs in {-1,0,1}. Normalize rational results to reduced fractions with positive denominators, omitting /1 for integers. Sign data and width-halving do not establish root existence or convergence to a root; a separate theorem and its hypotheses would be required. initial left=-2/1, right=6/1, halvings=1≥0. Give (left,right,halvings,(right−left)/2^halvings). This is the geometric width formula without an earlier zero-stop, not a function-value error."
      }
    }
  ],
  "steps": [
    {
      "id": "S001",
      "uses": [
        "G001"
      ],
      "before": "left=-2<right=6",
      "after": "all endpoints and midpoints are exact rationals",
      "relation": "implies",
      "rule_id": "ordered_bracket_data",
      "conditions": [],
      "explanation": {
        "zh-Hant": "先核對端點嚴格有序；這些是已提供的資料，不代表已呼叫某個未知函數。",
        "en": "Check strict endpoint order first;these are supplied data,not observations from an evaluated unknown function."
      },
      "reverse_audit": {
        "kind": "premise_and_result_audit",
        "explanation": {
          "zh-Hant": "回到原始資料與本步條件核對，不把單向推論誤稱等價。",
          "en": "Check against the original data and this step's premises; a one-way implication is not an equivalence."
        }
      },
      "arithmetic": null
    },
    {
      "id": "S002",
      "uses": [
        "G001",
        "S001"
      ],
      "before": "initial width := sub(6, -2)",
      "after": "initial width = 8",
      "relation": "calculation",
      "rule_id": "exact_rational_arithmetic",
      "conditions": [],
      "explanation": {
        "zh-Hant": "寬度按右減左計算，必為正。",
        "en": "Width is right minus left and is positive."
      },
      "reverse_audit": {
        "kind": "premise_and_result_audit",
        "explanation": {
          "zh-Hant": "以精確有理數重算 initial width，不以小數近似替代。",
          "en": "Recompute initial width with exact rational arithmetic, not rounded decimals."
        }
      },
      "arithmetic": {
        "operation": "sub",
        "inputs": [
          "6",
          "-2"
        ],
        "output": "8",
        "label": "initial width"
      }
    },
    {
      "id": "S003",
      "uses": [
        "G001",
        "S002"
      ],
      "before": "each actual halving changes w to w/2",
      "after": "after 1 halvings: w_k=w₀/2^1",
      "relation": "implies",
      "rule_id": "halving_width_induction",
      "conditions": [],
      "explanation": {
        "zh-Hant": "k=0保留原寬；每多做一次真正的二分，寬度再除以2。",
        "en": "k=0 preserves the width;each further actual halving divides it by2."
      },
      "reverse_audit": {
        "kind": "premise_and_result_audit",
        "explanation": {
          "zh-Hant": "回到原始資料與本步條件核對，不把單向推論誤稱等價。",
          "en": "Check against the original data and this step's premises; a one-way implication is not an equivalence."
        }
      },
      "arithmetic": null
    },
    {
      "id": "S004",
      "uses": [
        "G001",
        "S003"
      ],
      "before": "(2)^1",
      "after": "2^steps = 2",
      "relation": "implies",
      "rule_id": "integer_power",
      "conditions": [],
      "explanation": {
        "zh-Hant": "以非負整數次有限乘積精確計算，零次為多項式中的乘法單位元。",
        "en": "Evaluate the finite nonnegative-integer power exactly; exponent0 uses the polynomial multiplicative identity."
      },
      "reverse_audit": {
        "kind": "premise_and_result_audit",
        "explanation": {
          "zh-Hant": "回到原始資料與本步條件核對，不把單向推論誤稱等價。",
          "en": "Check against the original data and this step's premises; a one-way implication is not an equivalence."
        }
      },
      "arithmetic": {
        "operation": "integer_power",
        "inputs": [
          "2",
          "1"
        ],
        "output": "2",
        "label": "2^steps"
      }
    },
    {
      "id": "S005",
      "uses": [
        "G001",
        "S004"
      ],
      "before": "width after halvings := div(8, 2)",
      "after": "width after halvings = 4",
      "relation": "calculation",
      "rule_id": "exact_rational_arithmetic",
      "conditions": [],
      "explanation": {
        "zh-Hant": "分母2^k非零，所以可精確相除。",
        "en": "The denominator2^k is nonzero,so exact division is valid."
      },
      "reverse_audit": {
        "kind": "premise_and_result_audit",
        "explanation": {
          "zh-Hant": "以精確有理數重算 width after halvings，不以小數近似替代。",
          "en": "Recompute width after halvings with exact rational arithmetic, not rounded decimals."
        }
      },
      "arithmetic": {
        "operation": "div",
        "inputs": [
          "8",
          "2"
        ],
        "output": "4",
        "label": "width after halvings"
      }
    },
    {
      "id": "S006",
      "uses": [
        "G001",
        "S005"
      ],
      "before": "no function or stop record was supplied",
      "after": "this is geometric halving width,not a root-existence certificate",
      "relation": "implies",
      "rule_id": "width_scope",
      "conditions": [],
      "explanation": {
        "zh-Hant": "若因零符號提早停止並塌縮成一點，實際寬度可為0；不強迫再執行k次函數評估。",
        "en": "If a recorded zero causes an early singleton stop,the actual width may be0;this does not require k more function evaluations."
      },
      "reverse_audit": {
        "kind": "premise_and_result_audit",
        "explanation": {
          "zh-Hant": "回到原始資料與本步條件核對，不把單向推論誤稱等價。",
          "en": "Check against the original data and this step's premises; a one-way implication is not an equivalence."
        }
      },
      "arithmetic": null
    }
  ],
  "math_model": {
    "result": [
      "-2",
      "6",
      1,
      "4"
    ],
    "decision": "width_only"
  },
  "conclusion": {
    "canonical_value": "(-2, 6, 1, 4)",
    "explanation": {
      "zh-Hant": "依上列完整代值及條件核對得到原題答案；原題編號、格式與狀態保持不變。",
      "en": "The full substitutions and premise checks give the original answer; source identity,format and status are unchanged."
    }
  },
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    "zh-Hant": "沿用原題明示的論域、假設與來源 MKO 定義。本題已完成第二對話數理與中英語義覆核，並由原始參數逐題獨立重算模型、答案與每個算術步驟；原題仍為 candidate。",
    "en": "Use the original question domain, assumptions and cited MKO definitions. This item has second-context mathematical and bilingual review, with the model, answer and every arithmetic step independently recomputed from the original parameters; the source question remains a candidate."
  },
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      "en": "Source-bound pedagogical derivation candidate.Exact checking is not independent AI/human review or general formal proof.Original questions,answers,MKOs,formulas,ASTs and history remain unchanged."
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