Advanced MathHardValue at zero from a vertex and a point
Advanced Math practice question
A quadratic function f has its vertex at (2, −9), and its graph in the xy-plane passes through the point (5, 0). What is the value of f(0)?
Answer: -5
f(x) = a(x − 2)² − 9. At (5, 0): 9a − 9 = 0, so a = 1. Then f(0) = (0 − 2)² − 9 = −5.
Common wrong answers
- If you answered 5
- 5 has the wrong sign.
- If you answered -9
- −9 is the minimum value, at x = 2, not f(0).
- If you answered -13
- −13 comes from −4 − 9, using −(0 − 2)².
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