Matrices of linear transformations

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Homework Help Overview

The discussion revolves around finding the matrix representation of a linear operator T defined on the space of polynomials of degree at most 2, P2. The operator transforms a polynomial expressed in terms of the standard basis B = {1, x, x2} into a new form. Participants are exploring the implications of this transformation and how to express the polynomials in terms of the basis.

Discussion Character

  • Exploratory, Conceptual clarification, Problem interpretation

Approaches and Questions Raised

  • Participants are attempting to express the polynomial 1 in terms of the basis and are questioning the correct method to find the components of the polynomials x and x2. There is uncertainty about the transformation process and how to derive the matrix representation from the operator.

Discussion Status

The discussion is ongoing, with participants providing insights and corrections to each other's interpretations. Some guidance has been offered regarding the representation of polynomials in the basis, but there is still confusion about the correct approach to finding the components of the polynomials.

Contextual Notes

Participants are grappling with the definitions and representations of polynomials in the context of linear transformations, and there is a focus on ensuring clarity in the expressions used for the transformation.

derryck1234
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Homework Statement



Let T: P2 - P2 be the linear operator defined by
T(a0 + a1x + a2x2) = a0 + a1(x - 1) + a2(x - 1)2

(a) Find the matrix for T with respect to the standard basis B = {1, x, x2}.

Homework Equations



[T]B[x]B = [T(x)]B

The Attempt at a Solution



T(1) = a0 + a1(1 - 1) + a2(1 - 1)2
= a0

Okay...I don't know if I'm going in the right direction here?...and if I am, I'm not sure how to obtain vectors from the proceeding expressions for T(x) and T(x2)??

Any help would be appreciated.

Thanks.

Derryck.
 
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Hi Derryck! :smile:
derryck1234 said:
Let T: P2 - P2 be the linear operator defined by
T(a0 + a1x + a2x2) = a0 + a1(x - 1) + a2(x - 1)2

(a) Find the matrix for T with respect to the standard basis B = {1, x, x2}.

T(1) = a0 + a1(1 - 1) + a2(1 - 1)2
= a0

nooo :redface:

suppose it was T(a0 + a1x + a2x2) = a0 + a1(x + 1) + a2(x + 1)2

then your method would give you T(1) = a0 + a1(1 + 1) + a2(1 + 1)2
= a0 + 2a1 + 4a2

but the correct way is to start by saying 1 = 1 + 0x + 0x2, so T(1) = … :wink:

carry on from there :smile:
 
Wo...?

But then is this the same as saying (in vector form):

1 1
0 = 0
0 0 ?

I'm not sure what you mean by 1 = 1 + 0x + 0x2, because what I see from this, I would think that it would be more correct to say:

1 = a0 + a1x + a2x2, then to solve...? Flip, I'm so bad at this I know...but please, just humor me a little...it will help a great deal...

Cheers

Derryck
 
derryck1234 said:
I'm not sure what you mean by 1 = 1 + 0x + 0x2, because what I see from this, I would think that it would be more correct to say:

1 = a0 + a1x + a2x2, then to solve...?

Yes, and the solution is a0 = 1, a1 = a2 = 0, isn't it? :wink:

In other words: in the basis {1,x,x2}, 1 has components (1,0,0).

ok, now what are the components of x ?

and what are the components of x2 ? :smile:
 
Ok, the components of x would be found by solving:

x = a0 + a1(x - 1) + a2(x - 1)2

So I would then say

a1(x - 1) = x
Therefore a1 = x / (x - 1)... Am I going along the right lines? I'm not too sure what to do from here.

Thanks for the help so far though really!

Cheers

Derryck
 
derryck1234 said:
Ok, the components of x would be found by solving:

x = a0 + a1(x - 1) + a2(x - 1)2

No!

In the basis {1,x,x2}, what is x?

x = ?1 + ?x + ?x2
 

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