Advanced MathHardFinding a quadratic coefficient from two points
Advanced Math practice question
The graph of y = ax² + bx in the xy-plane passes through the points (1, 5) and (2, 14), where a and b are constants. What is the value of a?
Answer: 2
At (1, 5): a + b = 5. At (2, 14): 4a + 2b = 14, so 2a + b = 7. Subtracting the first equation from this gives a = 2 (and b = 3).
Common wrong answers
- If you answered 3
- 3 is b, not a.
- If you answered 5
- 5 is a + b.
- If you answered 7
- 7 is 2a + b.
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