We are given a quadratic function $f(x) = ax^2 + bx + c$, where $a, b, c$ are real numbers. The maximum value of $f(x)$ on the interval $-1 \le x \le 1$ is $M$, and the minimum value is $m$. We are given that $M = 1$ and $m = -1$. We need to find the coordinates of the vertex of the parabola $y = f(x)$ when $a = 1$, and determine the conditions on $b$ for $|-b/A| > 1$, which leads to $|b| > A$. Then we need to find the relationship between $|f(1) - f(-1)|$ and $|b|$ and $M - m$. Finally, we need to find the pairs $(b, c)$ that satisfy the given conditions.
2025/6/13
1. Problem Description
We are given a quadratic function , where are real numbers. The maximum value of on the interval is , and the minimum value is . We are given that and . We need to find the coordinates of the vertex of the parabola when , and determine the conditions on for , which leads to . Then we need to find the relationship between and and . Finally, we need to find the pairs that satisfy the given conditions.
2. Solution Steps
(1) When , . The vertex of the parabola is at . The -coordinate of the vertex is .
Thus, the vertex is . Therefore, A = 2 and B =
4. If $|-\frac{b}{A}| > 1$, then $|-\frac{b}{2}| > 1$, which means $|\frac{b}{2}| > 1$, so $|b| > 2$. Thus A =
2. Now we calculate $|f(1) - f(-1)| = |(1^2 + b(1) + c) - ((-1)^2 + b(-1) + c)| = |1 + b + c - (1 - b + c)| = |2b| = 2|b|$.
Since and , .
Thus, , and we are given . Therefore . Also, we have . Then, represents the equality. Thus corresponds to option 0 which is .
Since , and for , let us test the choices for (b, c).
Consider the case .
If (Option 0), . Then .
If (Option 1), . Then .
If (Option 2), . Then .
If (Option 3), . Then .
The vertex is at . Since , . This means the vertex is outside the interval . The maximum and minimum must occur at the endpoints and .
For option 3, , and . Also, and we have
In this case the minimum must be at x=
1. $f(1) = 1$. Thus $f(-1) > 1$. So $x= -1$ is neither maximum or minimum.
For option 1, .
The vertex is at .
Try . Then . Also
.
Consider and . Let E = 1, F =
2. $E < F$
3. Final Answer
A: 2
B: 4
C: 2
D: 0
E: 1
F: 2