Advanced MathHardCoefficient from the vertex's x-coordinate
Advanced Math practice question
The graph of y = x² + bx + 7 in the xy-plane has its vertex at x = −4. What is the value of b?
Answer: 8
The vertex of y = x² + bx + c is at x = −b/2, so −b/2 = −4 and b = 8.
Common wrong answers
- If you answered 4
- 4 forgets to double.
- If you answered -8
- −8 has the sign wrong.
- If you answered -4
- −4 copies the vertex's x-coordinate.
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