Advanced MathHardAxis of symmetry from standard form
Advanced Math practice question
In the xy-plane, the graph of y = 2x² − 12x + 5 is symmetric about the vertical line x = a. What is the value of a?
Answer: 3
The axis of symmetry is x = −b/(2a) = 12/(2 · 2) = 3.
Common wrong answers
- If you answered 5
- 5 is the constant term, unrelated to the axis.
- If you answered 6
- Divide by 2a = 4, not by 2: 12/4 = 3.
- If you answered -3
- With b = −12, the formula −b/(2a) gives +3.
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