Finding range of a function using inequalities

In summary, when given the functions ##f(x)## and ##g(x)## for ##-1.6 < x < 1.6##, the resulting interval for ##f(g(x))## should be ##[-3, -1.4)##. This may differ from other solutions depending on the question being asked. The inequality for ##f(x)## is split into two parts, ##0\leq f(x)< 1## and ##1\leq f(x)< 1.6##, to avoid ambiguity. The resulting solution may appear as two unique integers instead of an interval.
  • #1
JC2000
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Homework Statement
If ##f : R \Rightarrow R##and ##g:R \Rightarrow R## defined by ##f(x) = |x|## and ##g(x)=(x-3)## then ##{g(f(x)) : -1.6 < x < 1.6}##
Relevant Equations
Given ##f(x)## and ##g(x)## for ## -1.6 < x < 1.6## we get ##0\leq f(x)<1.6##
Now for ##0\leq f(x)< 1## ##\implies## ##g(f(x))=-3## since ## -3\leq f(x)-3<-2##
Again for, ##1\leq f(x)< 1.6## ##\implies## ##g(f(x))=-2## since ## -2 \leq f(x)-3 < -1.4##
Thus the required set is {-3,-2}
My attempt :

Given ##f(x)## and ##g(x)## for ## -1.6 < x < 1.6## we get ##0\leq f(x)<1.6##
Thus, for ##f(g(x))## we get ## -3 \leq g(f(x)) < -1.4##
Thus the required set should be the interval ##[-3, -1.4)##?

My Questions :
1. What have I missed since my answer does not match the given solution.
2. In the given solution why is the ##f(x)## inequality broken into ##0\leq f(x)< 1## and ##1\leq f(x)< 1.6##
3. After splitting the inequality I don't understand how the result is not an interval but two unique integers.
 
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  • #2
Your answer is correct given the problem stated. The other answer may be the answer to a different question.
 
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  • #3
JC2000 said:
My attempt :

Given ##f(x)## and ##g(x)## for ## -1.6 < x < 1.6## we get ##0\leq f(x)<1.6##
Thus, for ##f(g(x))## we get ## -3 \leq g(f(x)) < -1.4##
Thus the required set should be the interval ##[-3, -1.4)##?

My Questions :
1. What have I missed since my answer does not match the given solution.
2. In the given solution why is the ##f(x)## inequality broken into ##0\leq f(x)< 1## and ##1\leq f(x)< 1.6##
3. After splitting the inequality I don't understand how the result is not an interval but two unique integers.
You may want to use \mathbb r wrapped around in Latex for the Real numbers, instead of just R. It comes out like this ##\mathbb R##. In some cases you may eliminate ambiguity.
 
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1. What is the purpose of finding the range of a function using inequalities?

The range of a function using inequalities helps us determine the set of all possible output values of a function. This is important because it allows us to understand the behavior of a function and make predictions about its outputs.

2. How do you find the range of a function using inequalities?

To find the range of a function using inequalities, we first need to solve the inequality for the variable. Then, we can graph the solution on a number line to determine the range of the function. Alternatively, we can also use algebraic methods such as substitution or elimination to solve for the range.

3. What are the key differences between finding the range of a function using inequalities and using equations?

The main difference between the two methods is that inequalities allow for a range of values as opposed to a single value in equations. Inequalities also use symbols such as <, >, ≤, and ≥ to represent the relationship between the input and output values, while equations use an equal sign (=).

4. Can you explain the concept of an open interval and a closed interval in finding the range of a function using inequalities?

An open interval in finding the range of a function using inequalities refers to a range of values that does not include the endpoints. For example, (2, 5) would represent all values between 2 and 5, but not including 2 and 5. A closed interval, on the other hand, includes the endpoints. For example, [2, 5] would represent all values between 2 and 5, including 2 and 5.

5. When is it necessary to use inequalities to find the range of a function?

Inequalities are necessary when the range of a function is not a single value, but rather a set of values. This is often the case with functions that have a domain of all real numbers, or when the function has a non-linear relationship between the input and output values.

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