linearly

The plan

Roadmap

This page is a sequence, not a pile of links. Each stage says what to do, how long it takes, and how you will know you are done. If you only remember one thing: solving beats watching, every single week.

  • Nearly all of it free
  • About 150 hours
  • No calculus needed
  • Checkpoints at every stage

First, the method

How you study matters more than what you study. Every lecture here is built for the same five-step loop. It takes discipline for a week. Then it becomes a habit.

  1. 1Survey

    Flip through the slides once, fast. Two minutes. You are not learning yet. You are building a map so nothing later surprises you.

  2. 2Read, and redraw

    Read slowly. At each diagram, close it and draw it from memory, labels too. If you can't, read that part again. The drawing is the test.

  3. 3Run and predict

    Before you run each code block, say what it will print. Then change the numbers until something breaks, and look at what broke.

  4. 4Solve

    Do the exercises. Then a few MIT problems. Watch Strang only after you have solved. It lands better when you struggled first.

  5. 5Close the loop

    Explain the idea in five sentences to a friend. Tomorrow, derive the formula again. Next week, one more problem. That is what makes it permanent.

One warning. Watching lectures feels productive long before it is. Here, video comes after solving, as the reward for it.

What a week looks like

One hour a day, at the Stage 2 pace of two lectures a week. The schedule matters more than the hours.

  • MonSurvey and read one lecture. Redraw its figures.
  • TueRun its code. Do its exercises.
  • WedThree problems from the matching MIT set. Then watch Strang.
  • ThuSurvey and read the next lecture.
  • FriIts code and exercises.
  • SatExplain the week to a friend or a notebook. Re-derive the week's key formulas.
  • SunRest. Or one old exam question, if you feel like it.

Then, the path

  1. Prerequisites

    Before you start

    You need school algebra, the idea of a function, and enough Python to run a script. That is all. You do not need calculus. When a lecture wants an idea from calculus, it builds that idea on the spot.

    • Khan Academy, Algebrafree

      If solving 2x + 3 = 7 feels rusty, spend a weekend here first. Nothing else is missing.

    Done when: You can plot the point (2, 3) and solve 2x + 3 = 7 without thinking.

  2. Get the pictures

    Week 1. About 4 hours

    Watch Essence of Linear Algebra from start to finish before you study anything. No notes. No pausing to memorize. Let the animations put the core pictures in your head: vectors are arrows, matrices move space, determinants scale volume. Everything in this course hangs on those pictures.

    Done when: You can explain to a friend, waving your hands, what a matrix does to space.

  3. The course

    Months 1 to 3. About 80 hours

    Work through the lectures here in order, with the five-step method. One lecture every two or three days is a good pace. Speed is not the goal. Each lecture page names its matching Strang video and book sections, so pair them as you go.

    Done when: You can find a null space by hand, draw the four fundamental subspaces on a blank page, and say what least squares minimizes.

  4. Practice

    Every week, from week 2. About 30 hours

    Reading feels like understanding. Solving is understanding. Do problems from the first week on, and treat every wrong answer as the system working. At the end of each part of the course, sit a real MIT exam with the clock running and the book closed.

    Done when: You pass an archived Exam 1 with the book closed and the clock running.

  5. The bridge to AI

    Months 3 to 5. About 40 hours

    This is where the course pays off: the SVD, low-rank structure, PCA, and the linear algebra inside neural networks. Read Strang's data book next to Part VI of this course. Most of all, build things.

    Done when: You can write PCA in plain NumPy and defend every line.

  6. The rigorous second pass

    Whenever you want more

    Linear algebra rewards a second pass at a higher level. Axler rebuilds the subject through proofs. Trefethen and Bau rebuild it through computation. Pick the one that matches where you are going, or take both.

    Done when: You read a proof of the spectral theorem for fun.

When you are stuck

In this order. Most confusion dies at step one.

  1. 1.

    Draw the 2 by 2 case by hand. Most confusion cannot survive a small example. If it does, you found the real question.

  2. 2.

    Check it in NumPy. Ten seconds, no judgment. The computer settles arguments you are having with yourself.

  3. 3.

    Watch the matching recitation on 18.06SC. A different teacher, working a full problem. That is what recitations are for.

  4. 4.

    Read the same idea in Interactive Linear Algebra. A second telling with live figures. Often the second telling is the one that lands.

  5. 5.

    Ask on Math Stack Exchange. Show what you tried. Half the time you find the answer while writing the question.

The four ways people quit

Almost everyone who abandons this subject does it one of these ways. Name them and they lose most of their power.

  • Watching without solving. It feels like progress. It is not.

  • Memorizing steps instead of pictures. Steps decay in a week. Pictures last for years.

  • Skipping exercises because the reading made sense. Understanding you cannot use is not understanding yet.

  • Sprinting. Two lectures a day for a week, then nothing for a month. One hour a day beats both.

All along, build it yourself

Nothing proves understanding like implementation. When the course introduces an algorithm, write it before you call the library. The classic ladder: matrix multiplication, then LU, then QR, then eigenvalues by power iteration, then a small SVD. These sites turn the ladder into graded practice, in order, from NumPy to GPU kernels.

A good final project: eigenfaces. Load a face dataset, center it, compute the covariance, find the principal components with your own power iteration, and rebuild faces from twenty numbers. It uses everything in this course and fits in an afternoon.

Everything named here, plus the rest of the shelf, is in the library.