College Algebra / Unit 4 Alg 204 short lesson, about 20 seconds
The Lost-Root Error
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The idea
The lost-root error answers x² = k with √k alone; the negative root solves the equation too, and half the answer is missing.
In practice
For x² = 9, writing x = 3 abandons x = −3 — yet (−3)² = 9 checks as well as 3² does.
Where people slip
The principal-root convention governs the symbol, not the equation.
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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