Advanced MathHardEvaluating a quadratic after finding its leading coefficient
Advanced Math practice question
In the xy-plane, the graph of y = a(x − 2)(x − 6) passes through the point (4, −8), where a is a constant. What is the value of y when x = 8?
Answer: 24
At (4, −8): a(2)(−2) = −8, so a = 2. Then at x = 8: y = 2(6)(2) = 24.
Common wrong answers
- If you answered 2
- 2 is a, not the value of y.
- If you answered 12
- 12 uses a = 1.
- If you answered -24
- −24 has the wrong sign; (8 − 2)(8 − 6) is positive.
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