Linear Algebra › Section B · Matrix algebra › Topic B.2

The inverse of a matrix

To solve 5x = 15 you multiply both sides by 1/5. Some square matrices have a partner that undoes them in the same way, and finding that partner turns out to be ordinary row reduction in disguise.

In this topic

  • Undoing a matrix
  • Definition and uniqueness
  • The 2 × 2 formula
  • Solving a system with the inverse
  • Worked example: a 2 × 2 system
  • Rules for inverses
  • Elementary matrices
  • Why row reduction finds the inverse
  • Worked example: a 3 × 3 inverse
  • Common mistakes to avoid
  • Key takeaways

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