The graph of a function $f(x)$ is given. The function consists of a parabolic arc with vertex $V$, a line segment, and a portion of a homographic function. The domain of $f(x)$ is $\mathbb{R}$. We need to find the analytical expression for $f(x)$.
2025/6/29
1. Problem Description
The graph of a function is given. The function consists of a parabolic arc with vertex , a line segment, and a portion of a homographic function. The domain of is . We need to find the analytical expression for .
2. Solution Steps
Let's analyze the graph and determine the function for each part.
(a) Parabola: The vertex of the parabola is at . The general form of a parabola with vertex is . In our case, and , so . The parabola is defined for . When , we see that .
So, , which means , and thus .
The parabola is for .
(b) Line Segment: The line segment connects the point to the point . The equation of a line is . We can find the slope . Now we can use the point-slope form using the point :
, so .
This line segment is defined for .
(c) Homographic Function: This is a rational function of the form . There's a vertical asymptote at . This means when , so , or . So we have . The function passes through .
. So . As goes to infinity, the function appears to approach y=2 asymptotically. Thus , so . Substituting into gives , which implies , so .
Thus for .
Combining all the parts, we have:
$f(x) =
\begin{cases}
-x^2 - 4x - 3 & x \le -1 \\
\frac{1}{2}x + \frac{1}{2} & -1 < x \le 1 \\
\frac{2x}{x-1} & x > 1
\end{cases}$
3. Final Answer
$f(x) =
\begin{cases}
-x^2 - 4x - 3 & x \le -1 \\
\frac{1}{2}x + \frac{1}{2} & -1 < x \le 1 \\
\frac{2x}{x-1} & x > 1
\end{cases}$