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

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To prove that a function is affine if and only if it can be expressed as f(x) = Tx + b, where T is a linear transformation and b is a vector in W, one must start by understanding the definition of affine mappings. The hint to consider the mapping f - f(0) is crucial, as it allows the separation of the linear part from the constant offset. The proof involves showing that if f is affine, then the linear component T can be derived from the behavior of f around the origin. Additionally, it is essential to demonstrate that both T and b are uniquely determined by the function f. This establishes the relationship between affine functions and their representation in the specified form.
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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\rightarrowW such that

for all x,y\epsilonV and all \lambda\epsilon\Re.

QUESTION:
Prove that f:V\rightarrowW is affine if and only if it is of the form

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

where T:V\rightarrowW is linear and b\epsilonW. [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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