Mistake Master
Mistake Master · AP Precalculus · Unit 1 · Step-Through Animation
Zeros Come From the Top
You'll learnto see why a rational function's zeros come from its numerator and its forbidden inputs from its denominator.
A rational function has two floors and they do different jobs: the numerator decides where the value can be zero, the denominator decides where there is a value at all. Hand one the other’s job and a wall gets mistaken for a crossing. Watch the swap happen, then watch the domain check strike a candidate that looked perfectly good.
zeros from the top · domain from the bottom
Before you start
What you're looking at
A fraction with numerator and denominator color-coded for their two different jobs.
The question
When is the value of the fraction zero, and when is there no value at all?
Watch for
A numerator zero makes the function zero; a denominator zero forbids the input — and a domain check striking a tempting candidate.
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