Chapter 3: Problem 366
In the following exercises, (a) graph each function (b) state its domain and range. Write the domain and range in interval notation. $$ f(x)=2 x^{3} $$
Short Answer
Expert verified
For \( f(x) = 2x^3 \), domain: \( (-\infty, \infty) \), range: \( (-\infty, \infty) \).
Step by step solution
01
- Understand the function
The function provided is a cubic function of the form \( f(x) = 2x^3 \). This is a polynomial function, specifically a cubic function with a coefficient of 2.
02
- Determine key characteristics
Cubic functions have a general shape that includes a point of inflection around the origin. Since the coefficient is positive, the function will go from the third quadrant to the first quadrant of the coordinate plane.
03
- Create a table of values
Choose some values of \( x \) to compute corresponding \( f(x) \). For example: - \( x = -2 \), \( f(x) = 2(-2)^3 = -16 \) - \( x = -1 \), \( f(x) = 2(-1)^3 = -2 \) - \( x = 0 \), \( f(x) = 2(0)^3 = 0 \) - \( x = 1 \), \( f(x) = 2(1)^3 = 2 \) - \( x = 2 \), \( f(x) = 2(2)^3 = 16 \)
04
- Plot the points
Plot the computed points from the table on a coordinate grid. Points to plot: \((-2, -16)\), \((-1, -2)\), \((0, 0)\), \((1, 2)\), \((2, 16)\). Connect these points smoothly.
05
- Draw the function curve
After plotting the points, draw a smooth curve through each of the points to reflect the continuous nature of the polynomial function. This is the graph of \( f(x) = 2x^3 \).
06
- State the domain
The domain of any polynomial function is all real numbers. Therefore, the domain in interval notation is \( (-\infty, \infty) \).
07
- State the range
Since a cubic function goes to both infinities in the y-direction as x goes to plus or minus infinity, the range is also all real numbers. The range in interval notation is \( (-\infty, \infty) \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Understanding Cubic Functions
A cubic function is a type of polynomial function where the highest degree of the variable (usually represented by x) is 3. The general form of a cubic function is given by: [ f(x) = ax^3 + bx^2 + cx + d n this case, the function is simpler: [ f(x) = 2 x^3 Here’s what you need to know about cubic functions:
- They can have up to three real roots (where the function crosses the x-axis).
- They possess a point of inflection where the curve changes direction. In this example, the point of inflection is at the origin (0,0).
- The shape of a cubic function can vary, but typically, it will have an
Analyzing Domain and Range
The domain and range of a function are essential concepts in understanding how a function behaves. Let's break them down:
Domain: The domain of a function is the set of all possible input values (x-values) that the function can accept. For the cubic function given by 2x^3,
Range: The range of a function is the set of all possible output values (y-values) that the function can produce. For our cubic function:
Domain: The domain of a function is the set of all possible input values (x-values) that the function can accept. For the cubic function given by 2x^3,
- Since it's a polynomial function, there's no restriction on the x-values.
- This means that the domain is all real numbers, written in interval notation as (-∞, ∞)
Range: The range of a function is the set of all possible output values (y-values) that the function can produce. For our cubic function:
- As x approaches positive infinity, f(x) also approaches positive infinity.
- As x approaches negative infinity, f(x) approaches negative infinity.
- Therefore, the function can produce any y-value, making the range all real numbers, written as (-∞, ∞).
Plotting Points for the Graph
When graphing a function, it's helpful to plot points to understand the general shape of the curve. Follow these steps: 1. **Select x-values:** Choose a range of x-values to compute the corresponding f(x) values. For example, you can select -2, -1, 0, 1, and 2. 2. **Calculate f(x):** Use the function 2x^3 for each x-value:
- For x = -2, f(x) = 2(-2)^3 = -16
- For x = -1, f(x) = 2(-1)^3 = -2
- For x = 0, f(x) = 2(0)^3 = 0
- For x = 1, f(x) = 2(1)^3 = 2
- For x = 2, f(x) = 2(2)^3 = 16