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Question 280: Exact Solution of a Linear Equation

On this page
  1. Original question and givens
  2. Definition and scope
  3. Step-by-step derivation
  4. Reverse checks
  5. Result
  6. This question review and source binding

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P1000-0280 · q-20260927-linear-equation-exact-solve-0005

Original question and givens

Solve -1x+(13)=0 exactly over the rational numbers; a=-1 is explicitly nonzero.

  • G001 — Solve -1x+(13)=0 exactly over the rational numbers; a=-1 is explicitly nonzero.

Definition and scope

Use the rational domain with a≠0. Move the constant, divide by nonzero a and give the reduced fraction with positive denominator.

Step-by-step derivation

S001 · implies

Before

a=-1, b=13, x∈Q

After

equation: -1x+(13)=0

Conditions: none

Read the linear coefficient, constant and rational domain explicitly; a name alone does not establish nondegeneracy.

Step identifiers and dependencies

Rule: read_coefficients · Uses: G001

S002 · equivalent

Before

-1x+(13)=0

After

-1x=-13

Conditions: none

Subtract b from both sides, preserving the solution set.

Step identifiers and dependencies

Rule: subtract_constant · Uses: G001, S001

S003 · calculation

Before

x := div(-13, -1)

After

x = 13

Conditions: none

Division by a is allowed because -1≠0.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S002

S004 · calculation

Before

a·x := mul(-1, 13)

After

a·x = -13

Conditions: none

Substitute into the linear term.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S003

S005 · calculation

Before

a·x+b := sum(-13, 13)

After

a·x+b = 0

Conditions: none

Adding the constant must give0.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S004

S006 · implies

Before

a(x₁−x₂)=0 and a≠0

After

x₁=x₂

Conditions: none

Subtract equations for any two solutions and cancel nonzero a to prove uniqueness.

Step identifiers and dependencies

Rule: unique_solution · Uses: G001, S005

Reverse checks

  • S006 · premise_and_result_audit — Substitute into the original equation; retain every nonzero condition before division.
  • S005 · premise_and_result_audit — Recompute a·x+b with exact rational arithmetic, not rounded decimals.
  • S004 · premise_and_result_audit — Recompute a·x with exact rational arithmetic, not rounded decimals.
  • S003 · premise_and_result_audit — Recompute x with exact rational arithmetic, not rounded decimals.
  • S002 · premise_and_result_audit — Substitute into the original equation; retain every nonzero condition before division.
  • S001 · premise_and_result_audit — Substitute into the original equation; retain every nonzero condition before division.

Result

13

The full substitutions and premise audits recover the original answer, retaining its field order and verdict meanings.

This question review and source binding

Review date: 2026-10-26

Original questions, answers, step expressions, numeric ASTs and historical records are retained. Source candidate labels remain historical and are not overwritten as formal proof.

Source hashes and review receipts
  • input commit: 0f7be61e2c22317a4075561dc822c87d881a50db
  • original question SHA-256: a5cbcee96fa853f3f1ba998000701fc6fe5beb42ddf308e45b2d56769cf91877
  • candidate record SHA-256: 914e1cbd1fcea74a0ffc8cb270bf0af6e0c19f0c12fd38d24e628806c2bb6797
  • semantic review receipt SHA-256: 6c2c6d46aded7582a11ac41a8c0b3bdde2669a53bdb6e796eea2039994a02772
  • question-first witness SHA-256: 77e43898df9efdbf8094ad81fe4ab91cf4b4bd82f481eb9b4699b73cb4da612b
  • Lean: NOT_RUN · human review: NOT_PERFORMED
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