# StudyBrix

> Free practice questions, printable worksheets with answer keys, study guides, formula sheets and short self-study courses, from early learning (K–2) to university level.

Every course lesson has a Markdown version (append /index.md to the lesson URL). Subject and study-guide pages are plain HTML that is readable without JavaScript. Questions include their answers because this is a learning site, not a testing service; written responses and proofs come with sample answers for self-review.

## Start here

- [Worksheet builder](https://studybrix.com/en/): pick questions by subject, topic, grade and difficulty, then print a student copy and its answer key.
- [Subject library](https://studybrix.com/en/subjects): topics, sample exercises with answers, study guides and reference sheets.
- [Course catalogue](https://studybrix.com/en/courses): short courses with notes, worked examples and quizzes.

## Subjects

- [Astronomy & space](https://studybrix.com/en/subjects/astronomy)
- [Artificial intelligence](https://studybrix.com/en/subjects/ai)
- [Mathematics](https://studybrix.com/en/subjects/maths)
- [Reading & writing](https://studybrix.com/en/subjects/literacy)
- [Science](https://studybrix.com/en/subjects/science)
- [Physics](https://studybrix.com/en/subjects/physics)
- [Chemistry](https://studybrix.com/en/subjects/chemistry)
- [Biology](https://studybrix.com/en/subjects/biology)
- [Earth & space science](https://studybrix.com/en/subjects/earth)
- [Geography](https://studybrix.com/en/subjects/geography)
- [History](https://studybrix.com/en/subjects/history)
- [Language learning](https://studybrix.com/en/subjects/languages)
- [Computer science](https://studybrix.com/en/subjects/computing)
- [Life skills](https://studybrix.com/en/subjects/life)
- [Art & music](https://studybrix.com/en/subjects/arts)
- [Social studies](https://studybrix.com/en/subjects/social)
- [Study & wellbeing](https://studybrix.com/en/subjects/wellbeing)
- [Early learning](https://studybrix.com/en/subjects/early)
- [Environmental science](https://studybrix.com/en/subjects/environment)
- [Business & economics](https://studybrix.com/en/subjects/business)
- [Engineering & design](https://studybrix.com/en/subjects/engineering)
- [Media literacy](https://studybrix.com/en/subjects/media)
- [Music](https://studybrix.com/en/subjects/music)
- [Drama & speaking](https://studybrix.com/en/subjects/drama)
- [Physical education](https://studybrix.com/en/subjects/pe)
- [Philosophy & ethics](https://studybrix.com/en/subjects/ethics)

## Courses

- [University calculus and multivariable methods](https://studybrix.com/en/courses/university-calculus/index.md): Practise improper integrals, series, gradients and multiple integrals, with explicit conditions and worked examples.
- [Linear algebra: spaces, eigenvectors and fitting](https://studybrix.com/en/courses/linear-algebra/index.md): Develop matrix, vector-space and projection reasoning before using least squares.
- [Differential equations and numerical methods](https://studybrix.com/en/courses/differential-equations/index.md): Connect initial conditions, linear differential equations and numerical approximation with error and conditioning.
- [Probability models and continuous distributions](https://studybrix.com/en/courses/university-probability/index.md): Work with conditional probability, normalization, densities and expectation.
- [Real analysis: limits and rigorous reasoning](https://studybrix.com/en/courses/real-analysis/index.md): Build epsilon proofs and distinguish pointwise convergence, uniform convergence and compactness.
- [Abstract algebra and discrete proofs](https://studybrix.com/en/courses/algebra-and-discrete-proofs/index.md): Study groups, vector-space quotients and proof techniques with carefully scoped definitions.
- [Advanced mathematical methods](https://studybrix.com/en/courses/advanced-mathematical-methods/index.md): Study complex analysis, residues, Fourier series, PDE boundary conditions and convexity through focused lessons.
- [University mechanics and waves](https://studybrix.com/en/courses/university-mechanics/index.md): Connect rotation, oscillations, central forces and continuous wave models.
- [Fields, circuits and thermal physics](https://studybrix.com/en/courses/fields-and-thermal-physics/index.md): Work with Gauss laws, electrical field models, thermodynamic laws and electromagnetic waves.
- [Introduction to quantum physics and relativity](https://studybrix.com/en/courses/quantum-and-relativity/index.md): Compare relativistic measurement with quantum states, the Schrödinger equation and uncertainty.
- [Analytical and statistical mechanics](https://studybrix.com/en/courses/analytical-and-statistical-mechanics/index.md): Use Lagrangian and Hamiltonian methods, then interpret canonical ensembles.
- [Advanced physics methods and spacetime](https://studybrix.com/en/courses/advanced-physics-methods/index.md): Explore perturbation theory, scattering, variational quantum estimates and a conceptual bridge to general relativity.
- [Space and astronomy foundations](https://studybrix.com/en/courses/space-and-sky-foundations/index.md): Learn sky motion, the Solar System, astronomical light and safe telescope interpretation.
- [Stars, distances and stellar evolution](https://studybrix.com/en/courses/stellar-astronomy/index.md): Connect parallax, magnitudes and stellar structure to evolutionary paths and remnants.
- [Orbits, missions and exoplanets](https://studybrix.com/en/courses/orbits-missions-and-exoplanets/index.md): Explore two-body motion, spacecraft data, planet detection and atmospheric interpretation.
- [Astrophysics, cosmology and inference](https://studybrix.com/en/courses/astrophysics-and-cosmology/index.md): Study galaxy models, cosmic expansion, black holes and uncertainty in astronomical measurements.
- [AI foundations and responsible use](https://studybrix.com/en/courses/ai-foundations/index.md): Understand learning tasks, datasets, honest evaluation, privacy and human responsibility. No paid AI tool is required.
- [Mathematics of machine learning](https://studybrix.com/en/courses/machine-learning-mathematics/index.md): Work through regression, gradients, classification and generalization using paper-based examples.
- [Machine learning methods and validation](https://studybrix.com/en/courses/machine-learning-methods/index.md): Compare trees, clustering, PCA and validation without confusing training performance with evidence of generalization.
- [Neural networks, attention and embeddings](https://studybrix.com/en/courses/deep-learning/index.md): Build from artificial neurons and backpropagation to attention and embedding geometry.
- [Generative AI, RAG and practical evaluation](https://studybrix.com/en/courses/generative-ai-and-rag/index.md): Practise clear prompting, retrieval-grounded workflows, evidence checking and permission-aware deployment.
- [Python programming foundations](https://studybrix.com/en/courses/python-programming/index.md): Learn core Python concepts with paper-based reasoning and small code-reading tasks.
- [Web development foundations](https://studybrix.com/en/courses/web-development/index.md): Study HTML, CSS, JavaScript and accessible web structure without a paid bootcamp.
- [SQL and relational databases](https://studybrix.com/en/courses/sql-databases/index.md): Learn tables, queries, joins and data modelling with original exercises.
- [Data science foundations](https://studybrix.com/en/courses/data-science/index.md): Work through data cleaning, visualization, modelling and interpretation.
- [Cybersecurity foundations](https://studybrix.com/en/courses/cybersecurity/index.md): Study defensive security, privacy and risk management without offensive exploitation instructions.
- [Practical statistics and inference](https://studybrix.com/en/courses/statistics-foundations/index.md): Learn descriptive statistics, probability, sampling and inference with worked reasoning.
- [Financial accounting fundamentals](https://studybrix.com/en/courses/financial-accounting/index.md): Learn statements, double entry and basic analysis with fictional examples.
- [Spreadsheet skills](https://studybrix.com/en/courses/spreadsheets/index.md): Learn formulas, references, cleaning and charts for practical study and office work.
- [Project management foundations](https://studybrix.com/en/courses/project-management/index.md): Learn scope, scheduling, risk and communication through practical scenarios.
- [Academic writing and research](https://studybrix.com/en/courses/academic-writing/index.md): Learn research questions, source evaluation, argument structure and citation practice.
- [Digital marketing foundations](https://studybrix.com/en/courses/digital-marketing/index.md): Learn audiences, funnels, content, measurement and responsible experimentation.
- [Graphic design foundations](https://studybrix.com/en/courses/graphic-design/index.md): Learn hierarchy, typography, layout and accessible visual communication.
- [Research and study skills](https://studybrix.com/en/courses/research-and-study/index.md): Build retrieval, note-making, planning and evidence-checking skills for independent learners.

## Other languages

- [es](https://studybrix.com/es/subjects): subject library and worksheet builder in this language.
- [fr](https://studybrix.com/fr/subjects): subject library and worksheet builder in this language.
- [pt-BR](https://studybrix.com/pt-BR/subjects): subject library and worksheet builder in this language.

## Optional

- [About, editorial and privacy](https://studybrix.com/en/editorial): how the material is written and corrected, what is stored, and advertising.
- [Sitemap](https://studybrix.com/sitemap.xml)