Advanced MathHardVertex form to x-intercepts
Advanced Math practice question
The function h is defined by h(x) = (x − 4)² − 9. At which values of x does the graph of h cross the x-axis?
- A. 1 and 7Correct
- B. 4 and −9
- C. −1 and −7
- D. 4 only
Answer: A. 1 and 7
Set (x − 4)² = 9, so x − 4 = ±3, giving x = 1 or x = 7.
Why the other answers are wrong
- B. 4 and −9
- 4 and −9 are the vertex's coordinates, not the x-intercepts.
- C. −1 and −7
- −1 and −7 flip the signs; x − 4 = ±3 gives 1 and 7.
- D. 4 only
- x = 4 is where the vertex is, and h(4) = −9, not 0.
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