Integration Proof: Proving/Refuting |f(x)-g(x)| Integrable on [a,b]

In summary, the definition of integrability states that a function is integrable if it can be bounded between two finite numbers by finding the area under its curve over a given interval. To prove that |f(x)-g(x)| is integrable on [a,b], you must show that the upper and lower sums of the function converge to the same value as the interval size approaches zero. Proving integrability is important because it allows us to determine the area under a curve and find the definite integral of a function. However, the Intermediate Value Theorem cannot be used to prove integrability. There is a difference between absolute and uniform integrability, where absolute integrability means that the function f(x) is integrable on [a,b]
  • #1
Rony
1
0

Homework Statement



prove or refute : let f(x), g(x) be integrable functions on [a,b] so |f(x)-g(x)| integrable on a [a,b]

Homework Equations





The Attempt at a Solution


I'm pretty sure that it's right, I just can't find formal proof, someone can give me direction.
 
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  • #2
Welcome Rony,
Use the triangle inequality |f(x)-g(x)| <= |f|+|g| to prove finiteness & the fact that f-g can be approximated with the corresponding differences of step functions
approximating f & g.
 

What is the definition of integrability?

The definition of integrability states that a function is integrable if it can be bounded between two finite numbers by finding the area under its curve over a given interval.

How do you prove that |f(x)-g(x)| is integrable on [a,b]?

To prove that |f(x)-g(x)| is integrable on [a,b], you must show that the upper and lower sums of the function converge to the same value as the interval size approaches zero. This can be done by using the definition of integrability and evaluating the limit of the Riemann sums.

What is the importance of proving integrability?

Proving integrability is important because it allows us to determine the area under a curve and find the definite integral of a function. This is useful in many fields, such as physics, engineering, and economics, where finding the total amount or quantity is necessary.

Can you use the Intermediate Value Theorem to prove integrability?

No, the Intermediate Value Theorem cannot be used to prove integrability. This theorem is used to show that a continuous function takes on all values between two points, but it does not prove integrability.

What is the difference between absolute and uniform integrability?

Absolute integrability means that the function f(x) is integrable on [a,b] if the absolute value of the function is integrable on [a,b]. Uniform integrability means that the function f(x) is integrable on [a,b] if for any interval [c,d] within [a,b], the function is also integrable on [c,d].

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