Desmos Graphing Calculator
desmos.com
Type an equation and watch the curve, with a slider for every parameter
No sign-upOn device
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wolframalpha.com
Answers a maths, science or unit question typed as an ordinary sentence.
A computational engine rather than a search engine: ask it to integrate something, compare two chemicals, convert an obscure unit or work out the population density of a country and it computes an answer with charts and sources. It is still the fastest way to check a piece of algebra or a physical constant. Natural-language parsing is the weak point — a slightly odd phrasing gets you a confidently wrong interpretation.
Questions
A genuinely usable free tier with paid plans for volume or team features. Step-by-step working — the part students actually want — sits behind Wolfram Alpha Pro.
Yes. Wolfram Alpha sends your input to its own servers to process it. That is fine for public material; for anything containing personal data, use one of the on-device tools instead.
Step-by-step working — the part students actually want — sits behind Wolfram Alpha Pro.
Alternatives
Same category or same task, ordered by how closely they overlap.
desmos.com
Type an equation and watch the curve, with a slider for every parameter
duolingo.com
Turns a language into five-minute daily drills you will actually keep doing
khanacademy.org
Explains school maths and science one short video and one exercise at a time
wikipedia.org
Gets you oriented on almost any subject, with the sources listed at the bottom
apps.ankiweb.net
Schedules flashcard reviews for the day before you would have forgotten them
exercism.org
Practice exercises in 80-odd languages with free feedback from a human mentor