Required to prove that ∫f(x)dx[b, a] =∫f(x−c)dx [b+c, a+c]

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Homework Help Overview

The discussion revolves around proving the equality of two definite integrals involving a function f and a constant shift c. The original poster presents a statement requiring proof that the integral of f over the interval [b, a] is equal to the integral of f shifted by c over the interval [b+c, a+c].

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to demonstrate the equality using the properties of antiderivatives and definite integrals. Some participants question the validity of assuming that the antiderivative of f(x-c) is simply F(x-c) without further justification. Others suggest that this assumption needs to be proven, particularly by applying the chain rule and considering a substitution.

Discussion Status

The discussion is ongoing, with participants exploring the assumptions made regarding the antiderivative and the implications of the chain rule. There is no explicit consensus yet, but guidance has been offered regarding the need for a proof of the assumption made by the original poster.

Contextual Notes

Participants note that the original poster's formatting may hinder readability for some users, which could affect engagement in the discussion.

jodecy
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Homework Statement


required to prove that
∫()[, ] =∫(−) [+, +]

where f is a real valued function integrable over the interval [a, b]

Homework Equations



∫() [, ]=()−()

The Attempt at a Solution




∫() [b, a]=()−()

∫(−) [+, +]=(+−)−(+−)=()−()
∴∫()[, ] =∫(−) [+, +]

right i placed the interval in the [] brackets


is this correct?
 
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You just assumed that the antiderivative of f(x-c) is F(x-c). Why is that true?
 


i believe it was given in a lecture i had so i assumed is that a wrong assumption?
 


jodecy said:
i believe it was given in a lecture i had so i assumed is that a wrong assumption?

It's not a wrong assumption. It just needs to be proved. If F'(x)=f(x), why is F'(x-c)=f(x-c)? It's easy, but you should say why. Use the chain rule. In other language, they may expect you to prove this using the substitution u=x-c. Why is dx=du?
 
Last edited:
You are probably not aware, but the way you posted makes your post unreadable to at least XP Windows users using Chrome, IE & Opera, attachment shows what they see. It looks little bit better under Vista, but is still barely readable.

I have corrected thread subject.
 

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