Educational Disclaimer

Last updated 13 August 2026

The Directory is a study aid. This page sets out plainly what that does and does not mean.

It is not a substitute for your teacher

Curricula vary between countries, states, districts and individual classrooms. Notation, preferred methods, rounding conventions and even the definition of a term can differ from what you see here. Where this site and your teacher disagree, follow your teacher — they are marking your work.

Accuracy

Every explanation and worked example has been written and checked with care. That is not the same as being error-free. If you find a mistake, please report it through the Contact page and it will be corrected. We would much rather be told.

Do not rely on this site as the sole source for anything consequential — a graded assessment, a standardised test, or a professional calculation — without checking it against your own materials.

No guarantee of results

Using this Directory will not guarantee any particular grade, test score, placement or outcome. Learning depends on far more than the quality of an explanation, and we make no claims about how much anyone's results will improve. We also publish no statistics about student outcomes, because we have not measured any and inventing them would be dishonest.

Third-party videos

Videos are made by independent creators and are chosen because they explain a topic well. We do not control their content and have not verified every statement in every video. A creator's approach, notation or emphasis may differ from the written explanation on the same page. Neither is “wrong”; if they conflict in a way that matters, trust your course materials.

Academic integrity

This Directory is designed to help you understand a topic, which is why every page leads with an explanation rather than an answer. Using it to learn is exactly the point. Copying a worked example as your own submitted work, or using it during an assessment where outside resources are not permitted, is your responsibility and may violate your school's academic integrity policy.

Availability

The Directory is provided free and without any commitment to remain available, at a particular address, or in its current form. Third-party videos may be removed by their creators at any time without notice to us.