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Where does f(x) = (x squared - 9) divided by (x squared - 2x - 3) have a hole rather than an asymptote?
AAt x = -3
BAt x = -1
CAt x = 0
DAt x = 3
Answer & Solution
Correct answer: D. At x = 3
1. Factor top and bottom before deciding what each zero of the denominator does.
2. The numerator factors as (x - 3) times (x + 3).
3. The denominator factors as (x - 3) times (x + 1).
4. The factor (x - 3) is shared by both, so its zero marks a removable discontinuity.
5. Setting x - 3 to zero gives x equal to 3, which is where the hole sits.
6. The factor (x + 1) appears only in the denominator, so x equal to negative 1 is a vertical asymptote.
7. Answering x = -3 uses a numerator factor that never appears in the denominator, so it gives an x-intercept.
8. Answering x = -1 names the asymptote rather than the hole.
9. Answering x = 0 confuses the y-intercept with a discontinuity.
_Source: OpenStax Precalculus (CC BY 4.0), section 3.7 Rational Functions_
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