College Algebra / Unit 4 Alg 185 short lesson, about 20 seconds
Multiplying Complex Numbers
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The idea
Complex numbers multiply by distribution, with i² replaced by −1 wherever it appears.
In practice
(2 + 3i)(1 + 4i) runs FOIL: 2 + 8i + 3i + 12i² = 2 + 11i − 12 = −10 + 11i.
Where people slip
The i² step is where the arithmetic turns.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
Builds on
- Nothing. This is a starting point.
Unlocks
- Nothing yet depends on this.
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