Is T^n Linear When T is Linear?

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Homework Help Overview

The discussion revolves around the properties of linear transformations, specifically whether the composition of a linear transformation T, denoted as T^n, remains linear for natural numbers n. The original poster seeks assistance in proving this property.

Discussion Character

  • Exploratory, Mathematical reasoning, Problem interpretation

Approaches and Questions Raised

  • Participants discuss starting with specific cases, such as T^2, and question whether the linearity holds for sums of vectors. There is mention of using mathematical induction as a method to prove the general case.

Discussion Status

Some participants have provided guidance on how to approach the proof, including suggestions to clarify steps in the induction process. There is an ongoing exploration of the necessary conditions for the proof without reaching a definitive conclusion.

Contextual Notes

Participants note the importance of the definitions of linear transformations and the implications of the induction hypothesis in their reasoning. There is an acknowledgment of the need to prove both properties of linearity for sums and scalar multiplication.

cristina89
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Homework Statement


If T is a linear transformation, proof that Tn is a linear transformation (with nEN).


Homework Equations


I know that T is a linear application if:
T(u+v) = T(u) + T(v)
T(au) = aT(u)

The Attempt at a Solution


Actually I don't know how to start using these two affirmations. Can anyone help me with it?
I know how to do this when it has numbers, but then it comes to these kind of proofs, I don't know how to do this.
 
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Start with T2. Is it true that T2(u+v)=T2(u)+T2(v)? Note that T2(u+v) means T(T(u+v)).

ehild
 
You can do the general proof "by induction".
 
I'm trying to solve it by induction.

For n = 1 ok.

Assuming that's ok for n = k.

For n = k+1

I don't know if I'm doing it right in this part:

Tk+1 = Tk.T(u+v) = Tk.(T(u+v)) = Tk(T(u)) + Tk(T(v)). Can I just afirm that's ok since T(u+v) is an application and Tk is an application too?
 
I would have put in one more step. Tk(T(u+ v))= Tk(T(u)+ T(v)), using the "given" fact that T is linear, and then "= Tk(T(u))+ Tk(T(v))" using the "induction hypothesis" that Tk is linear.

And, of course, you now need to prove that Tn(au)= aTn(u) but that can be done the same way.
 

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