Using the Intermediate Value Theorem to Solve for x in Continuous Functions

  • Thread starter Thread starter LilTaru
  • Start date Start date
  • Tags Tags
    Theorem Value
Click For Summary

Homework Help Overview

The discussion revolves around the application of the Intermediate Value Theorem to continuous functions, specifically addressing two problems: finding an x in [0, 1] such that f(x) = x, and finding an x in [0, 1] such that f(x) = f(x + 1) for a continuous function on [0, 2] with f(0) = f(2).

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to utilize the Intermediate Value Theorem but expresses uncertainty about its application. They consider the implications of the function's bounds for part (a) and seek guidance on forming a new function g to facilitate the application of the theorem. Some participants suggest constructing g(x) as f(x) - x and explore the implications of its values at specific points.

Discussion Status

Participants are actively engaging with the problem, with some offering guidance on constructing the function g. There is a recognition of the potential usefulness of comparing g to a constant, and while confusion remains about the formulation of g, there is a productive exploration of its properties and implications.

Contextual Notes

The original poster indicates a lack of clarity regarding the application of the Intermediate Value Theorem and the formation of the function g. There is an emphasis on understanding the behavior of g at the endpoints of the interval, particularly g(0) and g(1).

LilTaru
Messages
80
Reaction score
0

Homework Statement



a) Suppose that f(x) is a continuous function on [0, 1] and 0 <= f(x) <= 1 for all x in [0, 1]. Show that there is an x in [0, 1] where f(x) = x.

b) Suppose that f(x) is a continuous function on [0, 2] with f(0) = f(2). Show that there is an x in [0, 1] such that f(x) = f(x + 1).

Homework Equations


The Attempt at a Solution



I assume I have to use the Intermediate Value Theorem, but I have no idea how to use it! For (a) I thought 0 <= f(x) <= 1 means since f(x) is between f(a) and f(b) then there exists a c or x in this question so that f(x) = x, but I have no idea! And for (b)... not a clue! Please help?!
 
Physics news on Phys.org
Try to construct a new function g from f, in such a way that answering the question means comparing g to a constant (so that it's easier to apply the intermediate value theorem).
 
Oh! Does that mean for (a) g(x) = f(x) - x? Or am I completely off track?!
 
It's a good thought -- run with it and see where you get to.
 
I am still very confused with how to form g(x)... it is still not making sense how to prove this question!
 
LilTaru said:
I am still very confused with how to form g(x)... it is still not making sense how to prove this question!

You already formed a good g(x) by setting g(x)=f(x)-x. If g(0)=0 then f(0)=0 and you are done. Otherwise g(0) is positive, right? What happens if g(1)=0? Suppose g(1) is not zero. What sign is it?
 

Similar threads

  • · Replies 11 ·
Replies
11
Views
2K
  • · Replies 1 ·
Replies
1
Views
1K
  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 20 ·
Replies
20
Views
3K
  • · Replies 14 ·
Replies
14
Views
3K
  • · Replies 8 ·
Replies
8
Views
1K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 26 ·
Replies
26
Views
3K
Replies
8
Views
2K