Advanced MathEasy–Mediumx-intercepts of a parabola
Advanced Math practice question
In the xy-plane, at which points does the graph of y = x² − 9 cross the x-axis?
- A. (3, 0) and (−3, 0)Correct
- B. (9, 0) and (−9, 0)
- C. (0, 3) and (0, −3)
- D. (0, −9) only
Answer: A. (3, 0) and (−3, 0)
On the x-axis y = 0: x² = 9, so x = ±3.
Why the other answers are wrong
- B. (9, 0) and (−9, 0)
- ±9 squares to 81; the roots of x² = 9 are ±3.
- C. (0, 3) and (0, −3)
- Points on the x-axis have y = 0, not x = 0.
- D. (0, −9) only
- (0, −9) is the y-intercept, where the graph crosses the y-axis.
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