Matrices

What this lesson covers

Matrices is a 11-part Class 9 Mathematics lesson. Each part makes one point and then hands over to the next, so it can be read in a sitting or picked up again at the part you stopped on. It defines the idea in plain words before using it, works through an example step by step, breaks the topic into its parts and compares them, shows where it is used outside the textbook, names the mistakes that cost marks in an exam, ends with a recap of what to remember.

How it begins

A matrix is a rectangular array of numbers arranged in rows and columns. Its order is written rows × columns: always in that sequence. A 2 × 3 matrix has 2 rows and 3 columnsSpecial types: Square, equal rows and columns. Identity (I): 1s on the leading diagonal, 0s elsewhere. Behaves like the number 1. Zero: all entries zero.

The 11 parts

1. What a matrix is
2. Adding and scalar multiplication
3. When multiplication is possible
4. Multiplying step by step
5. Order matters: AB ≠ BA
6. Determinant and inverse of a 2×2
7. Solving equations with matrices
8. Where matrices are used
9. Where marks are lost
10. What to remember
11. Watch one worked through