College Algebra / Unit 7 Alg 379 short lesson, about 20 seconds
The Erased-Hole Error
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The idea
The erased-hole error treats a simplified rational expression as sharing the original's domain; canceling a factor never re-admits the value that zeroed it.
In practice
The simplified (x − 3)/(x + 2) answers 6 at x = −3 — but the original divides zero by zero there. The 6 marks a hole, not a point.
Your place on the trail
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Builds on
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Unlocks
- Nothing yet depends on this.
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