Chapter 3: Problem 10
A function is given by a table of values, a graph, a formula, or a verbal description. Determine whether it is one-to-one. $$ f(x)=10-3 x $$
Short Answer
Expert verified
Yes, the function is one-to-one.
Step by step solution
01
Understanding One-to-One Function
A function is considered one-to-one if it never assigns the same value to two different inputs. In other words, for it to be one-to-one, if \( f(x_1) = f(x_2) \), then it must be that \( x_1 = x_2 \).
02
Analysis Using Algebraic Method
Consider the function \( f(x) = 10 - 3x \). To determine if it's one-to-one, assume \( f(x_1) = f(x_2) \). This implies \( 10 - 3x_1 = 10 - 3x_2 \). Simplifying, we get \(-3x_1 = -3x_2\) or further simplified, \( x_1 = x_2 \). This shows that the function is one-to-one because the equality holds only when \( x_1 = x_2 \).
03
Graphical Interpretation
The function \( f(x) = 10 - 3x \) is a linear function, represented graphically as a straight line with a negative slope. A linear function with a non-zero slope is always one-to-one because it passes the horizontal line test: no horizontal line intersects the graph more than once.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Linear Function
A linear function is a type of function that creates a straight line when graphed. It can be represented by the equation of the form \( f(x) = mx + b \) where:
Linear functions are simple because they have constant rates of change. This means for any equal changes in \( x \), the changes in \( f(x) \) will also be equal. In our particular function, \( f(x) = 10 - 3x \), the "-3" indicates the line has a negative slope, meaning it falls as \( x \) increases.
- \( m \) is the slope of the line
- \( b \) is the y-intercept
Linear functions are simple because they have constant rates of change. This means for any equal changes in \( x \), the changes in \( f(x) \) will also be equal. In our particular function, \( f(x) = 10 - 3x \), the "-3" indicates the line has a negative slope, meaning it falls as \( x \) increases.
Horizontal Line Test
The horizontal line test is a simple way to determine if a function is one-to-one. By applying the test to a graph, you draw horizontal lines across the graph and check how many times each line intersects with the graph.
- If any horizontal line crosses the graph more than once, the function is not one-to-one.
- If every horizontal line crosses the graph at most once, then the graph represents a one-to-one function.
Function Analysis
When performing function analysis to determine if a function is one-to-one, you examine its properties either graphically or algebraically. For algebraic analysis, if given \( f(x_1) = f(x_2) \), you solve to find whether \( x_1 = x_2 \). If they are always equal, it means the function is one-to-one.
In the given example, starting with \( f(x_1) = f(x_2) \) for \( f(x) = 10 - 3x \), simplifying reveals \(-3x_1 = -3x_2\), thus \( x_1 = x_2 \). Therefore, using algebraic reasoning, we confirm this function's one-to-one property.
In the given example, starting with \( f(x_1) = f(x_2) \) for \( f(x) = 10 - 3x \), simplifying reveals \(-3x_1 = -3x_2\), thus \( x_1 = x_2 \). Therefore, using algebraic reasoning, we confirm this function's one-to-one property.
Function Graph
A function graph visually represents the relationship between input values (x-axis) and output values (y-axis). In the case of the linear function \( f(x) = 10 - 3x \), the graph is a straight line.
To graph a linear function, you can use:
To graph a linear function, you can use:
- The y-intercept \( b \) as the starting point on the y-axis which is 10 in this case.
- The slope \( m \) (which is -3 here) to determine the next points. From the y-intercept, for each step of 1 unit move horizontally, move 3 units downward because the slope is negative.