Proving the Existence of f(x)=x: A Continuos Function Problem | [0,1]

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In summary, the conversation is discussing the existence of a value of x in the interval [0,1] such that a continuous function f(x) equals the value of x. The problem is simplified by considering a function g(x) with specific values at 0 and 1, and the question is whether g(x) must cross the x-axis somewhere in between. The solution involves defining a new function G(x) and considering its properties in relation to f.
  • #1
jmich79
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Homework Statement



Suppose that f is ais continuos function defined on [0,1] with f(0)=1 and f(1)=0. show that there is a value of x that in [0,1] such that f(x)=x. Thank You.
 
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  • #2
This is slightly simpler:
Let's say I have a function [itex]g:[0,1] \rightarrow \Re[/itex], which is continuous, with [itex]g(0)=1[/itex] and [itex]g(1)=-1[/itex] can you show that there is an [itex]x \in [0,1][/itex] so that [itex]g(x)=0[/itex]?
 
  • #3
Im Still Not Following. Can You Explain It A Little Bit Better To Me. Thank You For Your Post By The Way.
 
  • #4
If a function that's continuous is negative at one point, and positive at another point, does it necesarily cross the x-axis (i.e. is zero somewhere in between)?

That's what he's driving at, but puts it in terms that are more obviously applicable to the problem at hand
 
  • #5
Define the function G(x)=f(x)-x. Now four questions. i) is G continuous? ii) What are G(0) and G(1)? iii) What does it mean if G(x)=0 in terms of f? iv) Might this have something to do with the NateTG's and Office_Shredder's hints?
 

1. How can you prove that f(x)=x is a continuous function on the interval [0,1]?

To prove that f(x)=x is a continuous function on the interval [0,1], we can use the definition of continuity. This means showing that for any value of x in the interval [0,1], the limit of f(x) as x approaches that value is equal to the value of f(x) at that point. In other words, there are no sudden jumps or breaks in the function within the interval.

2. Can we use the Intermediate Value Theorem to prove the continuity of f(x)=x on [0,1]?

Yes, the Intermediate Value Theorem states that if a function is continuous on a closed interval [a,b] and takes on two values, then it must also take on all values in between those two values. In the case of f(x)=x, since it is a straight line, it will pass through every point between (0,0) and (1,1), thus satisfying the conditions of the Intermediate Value Theorem.

3. What is the graphical representation of f(x)=x on the interval [0,1]?

The graphical representation of f(x)=x on the interval [0,1] is a straight line passing through the points (0,0) and (1,1). This is because the function is defined as f(x)=x, meaning that the value of y (or f(x)) is always equal to the value of x within the interval.

4. Can we use the Mean Value Theorem to prove the continuity of f(x)=x on [0,1]?

No, the Mean Value Theorem only applies to differentiable functions, meaning that they have a defined derivative at every point within the interval. Since f(x)=x is a straight line, it has a constant derivative of 1 at every point, but it is not differentiable at the endpoints of the interval, making the Mean Value Theorem inapplicable in this case.

5. How does the continuity of f(x)=x on [0,1] relate to the notion of a "continuous function"?

The continuity of f(x)=x on [0,1] means that the function is defined and has no sudden breaks or jumps within the interval. This aligns with the concept of a "continuous function", which is a function that can be drawn without lifting the pen from the paper. In other words, there are no gaps or holes in the graph of the function, and it is defined at every point within the interval.

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