ACT Preparation / Unit 7 ACT 0619 short lesson, about 20 seconds
Matrices
Captions available
The idea
An m-by-n matrix has m rows and n columns. Same-size matrices add entry by entry, and AB exists only when A's column count equals B's row count.
In practice
A 2-by-3 times a 3-by-4 gives a 2-by-4; a 2-by-3 times a 2-by-3 is undefined.
Where people slip
Order matters: AB can exist while BA does not.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
Builds on
Unlocks
- Nothing yet depends on this.
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