Where linear algebra usually trips students up
Linear algebra rewards practice, yet the marks that decide a grade tend to slip away in the same few places.
- Computing without understanding. You can row-reduce a matrix perfectly and still struggle to say what a basis or a rank actually is, and that gap is where the harder marks live.
- The jump into abstraction. Moving from arrows in the plane to vector spaces of polynomials or functions, where a vector no longer looks like a list of numbers, unsettles almost everyone at first.
- Span, independence and basis blurring together. The three ideas are closely related but not the same, and keeping them distinct is half the battle in the early proofs.
- Confusing a linear map with its matrix. The same transformation has different matrices in different bases, and losing sight of that makes change of basis and diagonalisation feel arbitrary.
- Treating eigen-theory as mechanics only. Finding eigenvalues is routine; knowing why we diagonalise, and what to do when a matrix will not, is what the exam really tests.
- Hand-waving the short proofs. Much of the assessment is brief structural arguments, and marks are lost to vagueness rather than to hard computation.