Prove that a function is affine if and only if it is of the form f(x)=Tx+b

In summary, the conversation is about proving that an affine mapping from V to W is of the form f(x) = Tx + b, where T is a linear mapping and b is a vector in W. The hint given is to consider the mapping f-f(0) to prove the 'only if' part. It is mentioned that the examples on page 7 and 8 of the given notes use numbers, but the individual does not know how to do it without numbers.
  • #1
gilabert1985
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Hi, I have the following problem that is part of a project, and I have been stuck on it for the last couple of hours ... Thanks a lot for any help you can give me!

It says:

"An affine mapping from V to W, where W is a second real vector space, is a mapping f:V[itex]\rightarrow[/itex]W such that

for all x,y[itex]\epsilon[/itex]V and all [itex]\lambda\epsilon\Re[/itex].

QUESTION:
Prove that f:V[itex]\rightarrow[/itex]W is affine if and only if it is of the form

f(x)=Tx+b, ---> (this is formula (1))

where T:V[itex]\rightarrow[/itex]W is linear and b[itex]\epsilon[/itex]W. [Hint: to prove the 'only if' part, consider the mapping f-f(0).]

Show further that T and b in (1) are uniquely determined by f."

So I know the definition of affine functions from Wikipedia (http://en.wikipedia.org/wiki/Affine_transformation), so the hint I get that suggests me to consider the mapping f-f(0) makes sense. However, I have no clue how to do it without numbers (like it is done in the examples of page 7 and 8 of these notes http://cfsv.synechism.org/c1/sec15.pdf)
 
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FAQ: Prove that a function is affine if and only if it is of the form f(x)=Tx+b

How do you define an affine function?

An affine function is a mathematical function that can be expressed in the form f(x) = mx + b, where m and b are constants and x is the independent variable. This type of function represents a linear relationship between two variables, with a constant slope (m) and a y-intercept (b).

What is the difference between an affine function and a linear function?

An affine function is a type of linear function, but it includes an additional constant term (b). This means that an affine function can have a non-zero y-intercept, while a linear function always passes through the origin (0,0).

How do you prove that a function is affine?

A function can be proved to be affine if it can be written in the form f(x) = Tx + b, where T is a constant and b is a constant term. This means that the function has a constant slope and a non-zero y-intercept, which is a characteristic of affine functions.

What is the significance of the form f(x) = Tx + b in proving that a function is affine?

The form f(x) = Tx + b is significant because it represents the defining equation of an affine function. By showing that a function can be written in this form, it proves that the function is affine and has a linear relationship between its variables with a constant slope and a non-zero y-intercept.

Can a function be affine if it does not have the form f(x) = Tx + b?

No, a function cannot be affine if it does not have the form f(x) = Tx + b. The defining characteristic of an affine function is that it can be expressed in this form, so a function that cannot be written in this way is not considered to be an affine function.

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