Answer parts a-d for the function f(x) = x^3 - 3x^2 - x + 3. a) Use the leading coefficient test to determine the graph's end behavior. Which statement describes the behavior at th... Answer parts a-d for the function f(x) = x^3 - 3x^2 - x + 3. a) Use the leading coefficient test to determine the graph's end behavior. Which statement describes the behavior at the ends of f(x)? b) Find the x-intercepts and state their characteristics regarding the x-axis. c) Find the y-intercept. d) Use a graphing tool to graph the function and verify if it is drawn correctly using the maximum number of turning points.
Understand the Problem
The question is asking to analyze the function f(x) = x^3 - 3x^2 - x + 3 by using the leading coefficient test to determine its end behavior, find its x-intercepts and y-intercept, and graph the function. This involves both theoretical understanding and practical graphing skills.
Answer
Y-intercept: (0, 3); X-intercepts: (1, 0), (3, 0), (-1, 0). End behavior: down left, up right.
Answer for screen readers
The y-intercept is (0, 3) and the x-intercepts are (1, 0), (3, 0), and (-1, 0). The end behavior is down to the left and up to the right.
Steps to Solve
- Determine End Behavior using Leading Coefficient Test
The leading term of the function $f(x) = x^3 - 3x^2 - x + 3$ is $x^3$. Since the degree is odd and the leading coefficient is positive, the end behavior is:
- As $x \to -\infty$, $f(x) \to -\infty$
- As $x \to +\infty$, $f(x) \to +\infty$
- Find the Y-Intercept
To find the y-intercept, substitute $x = 0$ into the function:
$$ f(0) = 0^3 - 3(0^2) - 0 + 3 = 3 $$
Thus, the y-intercept is at the point $(0, 3)$.
- Find the X-Intercepts
To find x-intercepts, set $f(x) = 0$ and solve:
$$ x^3 - 3x^2 - x + 3 = 0 $$
We can use the Rational Root Theorem to test potential rational roots: factors of $3$ (constant term). Testing $x = 1$:
$$ f(1) = 1^3 - 3(1^2) - 1 + 3 = 0 $$
Thus, $x = 1$ is a root.
Now, use synthetic division to factor $f(x)$ by $(x - 1)$:
Performing synthetic division of $f(x)$ by $(x - 1)$ gives:
$$ f(x) = (x - 1)(x^2 - 2x - 3) $$
Next, factor the quadratic:
$$ x^2 - 2x - 3 = (x - 3)(x + 1) $$
Combining this gives:
$$ f(x) = (x - 1)(x - 3)(x + 1) $$
Thus, the x-intercepts are $x = 1$, $x = 3$, and $x = -1$.
- Graph the Function
Using the information gathered:
- End behavior: Down to the left, up to the right.
- Y-intercept: (0, 3)
- X-intercepts: (1, 0), (3, 0), (-1, 0)
Plot these points and sketch the graph according to the end behavior and the x-intercepts.
The y-intercept is (0, 3) and the x-intercepts are (1, 0), (3, 0), and (-1, 0). The end behavior is down to the left and up to the right.
More Information
This function describes a cubic polynomial. Its shape is determined by its degree and leading coefficient, categorized by having one or no turning points between its intercepts. The function will cross the x-axis three times, confirming the presence of three x-intercepts.
Tips
- Forgetting to check for all possible rational roots can lead to incomplete intercepts.
- Misapplying the end behavior of cubic functions can confuse students; remember the sign of the leading coefficient and the degree.
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