data/knowledge_base/linear_algebra.md

# Linear Algebra – Basics

## Matrix Addition
Possible only if matrices have same order

## Matrix Multiplication
- Order matters (AB ≠ BA)
- Columns of A must match rows of B

## Determinant (2×2)
|a b|
|c d| = ad − bc

## Inverse Exists If
det(A) ≠ 0

## Common Mistakes
- Multiplying matrices in wrong order
- Using inverse when determinant is zero