How this solver works
Most AI maths tools ask a language model to do the arithmetic. Language models are unreliable at exactly that: they can state a method correctly and still execute it wrongly, and they tend to be confident either way. So this solver does not work that way.
Your problem is parsed and handed to SymPy, a computer algebra system. SymPy computes the answer. Each step is then a claim that two expressions are equal, and that claim is tested by evaluating both at a dozen random points. Steps that pass are marked checked. A step that can be shown to be wrong is discarded rather than printed.
When it says it cannot check something
Some things genuinely cannot be verified automatically — proving two expressions equal is undecidable in general, and integration constants, domain restrictions and branch cuts all create honest ambiguity. When that happens the page says the step was not checked. It does not say the step is wrong, because that is not what it knows.
A written question the engine's own grammar cannot read is handed to an AI interpreter — you see that happen on screen, clearly labelled, and every concrete equality its answer relies on is machine-checked before you read it. Anything that genuinely needs a diagram has no route at all; when nothing can answer, the solver says so and points you at the relevant calculator instead.
Privacy
The calculators on this site run entirely in your browser. The solver is different — it sends your problem to our server, and for photos, word questions our engine cannot read, and plain-English explanations, to Google's Gemini as well — where the free tier's terms allow the content to improve Google's models and to be read by human reviewers. Please do not put personal information into the solver; the privacy page explains exactly what happens to it.