Domain & Range of Inverse Function f-1: x≤0, y≤0

In summary, the function f:x→ 4-x2 has an inverse denoted by f-1 with a domain of x≤4 and a range of y≤0. The graph of f is a parabola opening downwards with a restricted domain of x≤0. The inverse of f has a domain of x≤4 and a range of y≤0.
  • #1
FlopperJr
29
0

Homework Statement



The function f:x→ 4-x2 for the domain x≤0. Find the inverse of is denoted by f-1 and state the domain and range of f-1.

Homework Equations


Set equation to 0 and solve for x to find inverse. The D and R is going to be switched for the inverse..?


The Attempt at a Solution


I think I have found the inverse and range for this problem:
f-1(x) = -√4-x

and has a range of y≤0 (which was given in problem)

not sure of range. Are my solutions correct?
 
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  • #2
FlopperJr said:

Homework Statement



The function f:x→ 4-x2 for the domain x≤0. Find the inverse of is denoted by f-1 and state the domain and range of f-1.

Homework Equations


Set equation to 0 and solve for x to find inverse. The D and R is going to be switched for the inverse..?


The Attempt at a Solution


I think I have found the inverse and range for this problem:
f-1(x) = -√4-x

and has a range of y≤0 (which was given in problem)

not sure of range. Are my solutions correct?
You should really put 4-x in parentheses (or use LaTeX):
f -1(x) = -√(4-x)
The Range of f -1(x) is the same as the Domain of f(x). You are correct about this.

Do you know the Range of f(x) ?
 
  • #3
No, That is my problem. I tried but I keep getting wrong answer. 4-x^2=0
x=+/-2
 
  • #4
FlopperJr said:
No, That is my problem. I tried but I keep getting wrong answer. 4-x^2=0
x=+/-2

How would you describe the graph of y = 4-x2 ?
 
  • #5
SammyS said:
How would you describe the graph of y = 4-x2 ?

Its a parabola. It opens down, with the max point on 4.
 
  • #6
But you have a restricted domain, with x <= 0.
 
  • #7
I believe the domain and range of the inverse is
x>4 and y≤0
 
Last edited:
  • #8
The domain of f is {x | x <= 0}
The range of f is what? You know what the graph of f looks like, so you should be able to answer that by looking at the graph.

Then look at what SammyS said in post #2 about the domain and range of f-1.
 
  • #9
Okay thanks! I know that it is going to be oppsite of whatever the original function was.
Now that I see the graph, it would be x≤4.
 
  • #11
Thanks so much for your help! I always have trouble with the domain and range.
 

1. What is the domain of the inverse function f-1?

The domain of the inverse function f-1 is all real numbers less than or equal to 0 (x≤0).

2. What is the range of the inverse function f-1?

The range of the inverse function f-1 is all real numbers less than or equal to 0 (y≤0).

3. How is the domain of f-1 related to the range of the original function f?

The domain of f-1 is the same as the range of the original function f, and vice versa. This is because the inverse function is essentially the "flipped" version of the original function, so the x-values that were in the range of f become the y-values in the domain of f-1.

4. Can the inverse function f-1 have a different domain and range than the original function f?

Yes, it is possible for the inverse function f-1 to have a different domain and range than the original function f. This can happen when the original function f is not one-to-one, meaning that more than one input can produce the same output. In this case, the inverse function f-1 may have a restricted domain and range in order to maintain its one-to-one nature.

5. How can you graph the inverse function f-1 with a restricted domain and range?

If the inverse function f-1 has a restricted domain and range, you can graph it by first graphing the original function f, then reflecting it over the line y=x. Next, you can use the restricted domain and range to "cut off" any parts of the graph that fall outside of the given range. This will give you the graph of the inverse function f-1 with the restricted domain and range.

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