Advanced MathHardInput at a parabola's minimum
Advanced Math practice question
The function g(x) = x² − 4x + 7 reaches its minimum value at x = a. What is the value of a?
Answer: 2
The vertex of x² − 4x + 7 sits at x = −(−4)/(2 · 1) = 2.
Common wrong answers
- If you answered 3
- 3 is g(2), the minimum VALUE; the input where it occurs is x = 2.
- If you answered 4
- 4 is the coefficient b's magnitude; halve it (and flip sign): x = 2.
- If you answered -2
- x = −b/(2a) with b = −4 gives +2.
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