Learn

Learning preferences

Make learning more comfortable. Changes apply immediately.

Enlarges page content, including diagrams and their labels. You can also use your browser’s zoom.

Choose the colours that are easiest for you to distinguish. Applies to lesson diagrams and lab plots. Labels, shapes, hatching and line patterns also distinguish meanings. Source photographs and raw image brightness stay unchanged; mask-only views are available for image overlays.

ExampleComparisonSample link

Saved in this browser on this device. Preferences are separate from progress backups.

Mathematics · unit version 1

Binary gcd and integer certificates

Prove halving and subtraction rules, preserve integer Bezout coefficients, and distinguish a plausible answer from an independently checkable gcd certificate.

Open any lesson. Completion records participation; automatic practice checks and human judgment of written arguments are separate. This unit retains its own versioned requirements.

Readiness and preparation

Check your starting point

Try these short questions on paper, then compare your reasoning. They are optional self-checks, not a placement score or a navigation requirement. Use a targeted review when useful and return with your browser’s Back control.

Does a linear combination alone certify the greatest common divisor?

Coefficient tracking and gcd preservation are separate obligations.

Compare reasoning and find a refresher

No. The positive proposed gcd must also divide both inputs. Together, common divisibility and an integer linear-combination identity certify the greatest common divisor.

Review Euclid and Bezout certificates

Does an invariant alone prove that an algorithm stops?

Swapping values preserves their gcd but can repeat forever.

Compare reasoning and find a refresher

No. Supply a strictly decreasing nonnegative integer potential or another well-founded argument, and check the terminal condition separately.

Review invariants and termination

Loading saved mathematics work…

Repair the trace and certify the result

The mixed assessment has separate response history and review criteria; it does not change lesson participation records.

Lesson sequence

Each linked lesson opens on its own page. Expand its details here when you want to check the objectives before choosing.

  1. Binary gcd: preserve the value and prove termination

    Lesson details and objectives

    Replace division by guarded halving and subtraction, tracking an external power of two and a decreasing integer potential.

    • Prove the parity-sensitive halving and subtraction identities rather than applying halving unconditionally.
    • Maintain gcd(A,B)=s·gcd(u,v) through a complete trace, with zero and equality handled explicitly.
    • Prove termination for every permitted branch and distinguish a decreasing potential from a bit-complexity claim.

    6 practice tasks.

  2. Track integer Bézout coefficients through binary gcd

    Lesson details and objectives

    Normalize a common power of two, repair odd coefficient rows before halving, and verify the final gcd with an independent arithmetic certificate.

    • Maintain both linear-combination identities under subtraction and both halving branches.
    • Prove the repair coefficients are integers in every normalized-base parity case.
    • Recover coefficients for the original inputs and distinguish an identity from a complete gcd certificate.

    6 practice tasks.