16Hit1600
Advanced MathVery hardSum of the zeros of a vertex-form quadratic

Advanced Math practice question

The function f is defined by f(x) = −(x − 4)² + 9. What is the sum of all values of x for which f(x) = 0?

Answer: 8

(x − 4)² = 9 gives x = 1 or x = 7, which sum to 8.

Common wrong answers

If you answered 4
4 is the x-coordinate of the vertex, half the sum.
If you answered 6
6 is the difference of the zeros.
If you answered 7
7 is the larger zero alone.

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