Courses
Every lesson is free to read. A course adds a quiz at the end of each unit, a final exam that is marked and then checked by a person, and feedback that shows the line where your working went wrong.
Discrete Mathematics
Logic, proof, induction, relations, counting, recurrences, graphs, automata and complexity: the discrete maths of a first university course.
CollegeCalculus
Limits, derivatives, integrals and series: the single-variable calculus of a first university course.
GraduatePartial Differential Equations
Transport, heat, wave and Laplace equations, Fourier methods, energy and maximum principles, weak derivatives, Sobolev spaces, well-posedness and scaling.
GraduateFluid Dynamics
From the continuum hypothesis to the regularity theory of the incompressible Navier-Stokes equations.
How a course works
- Read the lessons in order. They are the same free lessons as the rest of the site, grouped into units.
- Take the quiz at the end of each unit. It is marked the moment you submit, with the worked solution for every question. The first unit's quiz is free.
- Pass every unit and sit the final. Answers the algebra system can check are marked by it; written proofs and photos of your working are read by a model and then reviewed by a person before your result is released.
- Wherever you went wrong, the result shows the line where it happened and why.
Prices
Course pass
$39
Every unit quiz, the final exam with one retake, and 20 checks of your own working, for one course.
One final exam
$15
A single sitting of one course's final, marked and reviewed. For someone who already knows the material and wants it tested.
Every course
$19/mo
All quizzes and finals in every course (two finals per course a month) and 100 working checks a month. Cancel from your account.
SubscribeWorking checks
$9
Ten checks: upload a photo of any working, or type it, and see where it went wrong.
Buy ten checks