Advanced MathMediumVertex of a parabola after reflection across the y-axis
Advanced Math practice question
In the xy-plane, the graph of y = (x − 3)² is reflected across the y-axis. What is the x-coordinate of the vertex of the reflected graph?
Answer: -3
Reflecting across the y-axis replaces x with −x: y = (−x − 3)² = (x + 3)². The vertex moves from (3, 0) to (−3, 0).
Common wrong answers
- If you answered 0
- 0 is the vertex's y-coordinate.
- If you answered 3
- 3 is the vertex of the original graph.
- If you answered 9
- 9 is the y-intercept of both graphs.
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