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

1. Apr 1, 2012

### jodecy

1. The problem statement, all variables and given/known data
required to prove that
∫()[, ] =∫(−) [+, +]

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

2. Relevant equations

∫() [, ]=()−()

3. The attempt at a solution

∫() [b, a]=()−()

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

right i placed the interval in the [] brackets

is this correct?

2. Apr 1, 2012

### Dick

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

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

3. Apr 1, 2012

### jodecy

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

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

4. Apr 1, 2012

### Dick

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

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: Apr 1, 2012
5. Apr 2, 2012

### Staff: Mentor

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.