How to Define a Piecewise Function Without Absolute Value Bars?

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In summary: The function $f(x)=x^2-1$ is always negative on $(-1,1)$, and changes sign at the endpoints. So we can define $|f(x)|$ as:|f(x)|=\begin{cases}1-x^2 & |x|<1 \\ x^2-1 & |x|\ge 1 \\ \end{cases}In summary, the function piecewise without absolute value bars can be defined as |f(x)|=1-x^2 for |x|<1 and x^2-1 for |x|>=1. This definition is based on the fact that the core function, f(x)=x^2-1, is negative on the interval (-
  • #1
paulmdrdo1
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Define the function piecewise without absolute value bars

f(x)=|x^2-1| - what is the core or prevailing function here? is it the absolute value function or the squaring?

please solve this. and show the steps. thanks!
 
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  • #2
Re: define the function...

I would use the definition:

\(\displaystyle |x|\equiv\begin{cases}-x & x<0\\ x & 0\le x \\ \end{cases}\)

So, what you want to find, is where the function \(\displaystyle f(x)=x^2-1\) is negative, and where is it non-negative.
 
  • #3
Re: define the function...

MarkFL said:
I would use the definition:

\(\displaystyle |x|\equiv\begin{cases}-x & x<0\\ x & 0\le x \\ \end{cases}\)

So, what you want to find, is where the function \(\displaystyle f(x)=x^2-1\) is negative, and where is it non-negative.

i have two answers

f(x) = {x^2-1 , if x<-1
...{0 , if x=-1 or x=1
...{1-x^2, if -1<x<1

or

f(x) = {x^2-1 , if x<=-1
...{1-x^2, if -1<x<1
...{x^2-1, if x>=1

are they both correct?
 
  • #4
Re: define the function...

The second one is correct...do you see why the first is not?

The function $f(x)=x^2-1$ is negative on $(-1,1)$, otherwise is is non-negative, so another way we could define $|f(x)|$ is:

\(\displaystyle |f(x)|=\begin{cases}1-x^2 & |x|<1 \\ x^2-1 & 1\le|x| \\ \end{cases}\)
 
  • #5
Re: define the function...

MarkFL said:
The second one is correct...do you see why the first is not?

The function $f(x)=x^2-1$ is negative on $(-1,1)$, otherwise is is non-negative, so another way we could define $|f(x)|$ is:

\(\displaystyle |f(x)|=\begin{cases}1-x^2 & |x|<1 \\ x^2-1 & 1\le|x| \\ \end{cases}\)

i based my first answer on this definition of abs. value function.

|x|= { x, if x>0
...{ 0, if x=0
...{ -x, if x<0
 
  • #6
Re: define the function...

You left out $1\le x$. Also, we really don't see special cases for when the expression is equal to zero, we just need to differentiate between negative and non-negative.
 
  • #7
Re: define the function...

MarkFL said:
You left out $1\le x$. Also, we really don't see special cases for when the expression is equal to zero, we just need to differentiate between negative and non-negative.

oh i see. but what if i add that x>1 to my first answer?

f(x) = {x^2-1 , if x<-1
...{0 , if x=-1 or x=1
...{1-x^2, if -1<x<1
...{x^2-1, if x>1

would this be correct? I just want to explore on the different possible answers. please bear with me.
 
  • #8
Re: define the function...

Yes, that would be correct, albeit not the most efficient piecewise statement of the function though.
 

FAQ: How to Define a Piecewise Function Without Absolute Value Bars?

What is the function of a scientific experiment?

The function of a scientific experiment is to test a hypothesis or to gather data that can be used to support or refute a scientific theory. It allows scientists to make observations, collect data, and draw conclusions based on evidence.

What is the purpose of defining a function in scientific research?

The purpose of defining a function in scientific research is to clearly define the role or purpose of a particular process or mechanism within an experiment. This allows for better understanding and interpretation of the results.

How do you define a function in a scientific experiment?

A function is defined in a scientific experiment by describing its specific role or purpose within the experiment and how it relates to the overall goal or hypothesis being tested. This can include the variables involved, the methods used, and the expected outcome.

Why is it important to define a function in a scientific experiment?

Defining a function in a scientific experiment is important because it helps to ensure that the experiment is well-designed and that the results are accurate and reliable. It also allows for better communication and replication of the experiment by other scientists.

Can a function change in a scientific experiment?

Yes, a function can change in a scientific experiment if new evidence or data suggests that the original function was incorrect or incomplete. This is a normal part of the scientific process and allows for the development and refinement of scientific knowledge.

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