Linear Algebra - Linear transformations

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Homework Help Overview

The discussion revolves around identifying which of the provided functions are linear transformations in the context of linear algebra. The functions in question are L(x,y,z) = (0,0), L(x,y,z) = (1,2,-1), and L(x,y,z) = (x^2 + y, y - z).

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Participants discuss the criteria for linear transformations, specifically the properties L(u + v) = L(u) + L(v) and L(ku) = kL(u). There is uncertainty about how to apply these properties to the given functions.

Discussion Status

Some participants have begun to explore specific examples to test the linearity of the transformations, particularly focusing on the first function. Others express confusion about the application of the transformation definitions and seek clarification on how to approach the problem.

Contextual Notes

Participants note a lack of understanding regarding the transformations themselves and how they relate to the linearity conditions. There is mention of using specific vectors to test the properties, but no consensus has been reached on the outcomes for all functions.

superdave
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Homework Statement



which of the following are linear transformations.

a) L(x,y,z) = (0,0)
b) L(x,y,z) = (1 ,2, -1)
c) L(x,y,z) = (x^2 + y, y - z)

The Attempt at a Solution



I know that L is a linear transformation if L(u + v) = L(u) + L(v) and L(ku) = kL(u).

I am not sure how to apply that to those equations.

Please help.
 
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superdave said:

Homework Statement



which of the following are linear transformations.

a) L(x,y,z) = (0,0)
b) L(x,y,z) = (1 ,2, -1)
c) L(x,y,z) = (x^2 + y, y - z)

The Attempt at a Solution



I know that L is a linear transformation if L(u + v) = L(u) + L(v) and L(ku) = kL(u).

I am not sure how to apply that to those equations.

Please help.
Start with a couple of vectors, say u = <x1, y1, z1> and v = <x2, y2, z2>.

For a), see if L(u + v) = L(u) + L(v) and L(ku) = kL(u). Do the same for b) and c).
 
Mark44 said:
Start with a couple of vectors, say u = <x1, y1, z1> and v = <x2, y2, z2>.

For a), see if L(u + v) = L(u) + L(v) and L(ku) = kL(u). Do the same for b) and c).

I guess my problem is, I don't know how to apply that to L(x,y,z) = (0,0). If it was L(v) = Av I would understand. I just don't understand the transformations themselves and how to apply them.
 
Well if it was L(v)=Av it wouldn't be interesting to ask if the transformation was linear!

For example for the first one if (x,y,z)=(1,2,4)

L(1,2,4)=(0,0).

And if (x,y,z)=(1,1,1)

L(1,1,1)=(0,0)

So L(1,2,4)+L(1,1,1)=(0,0)+(0,0)=(0,0).

Is this equal to L(2,3,5)? ((1,2,4)+(1,1,1))
 
Office_Shredder said:
Well if it was L(v)=Av it wouldn't be interesting to ask if the transformation was linear!

For example for the first one if (x,y,z)=(1,2,4)

L(1,2,4)=(0,0).

And if (x,y,z)=(1,1,1)

L(1,1,1)=(0,0)

So L(1,2,4)+L(1,1,1)=(0,0)+(0,0)=(0,0).

Is this equal to L(2,3,5)? ((1,2,4)+(1,1,1))

Ok, I think I understand. so that is linear because L(2,3,5) = (0,0). And L(ku) = kL(u) = (0,0).

But for b), the second part doesn't hold up because L(ku) = (1,2,-1) but kL(u) = k(1,2,-1) and they are not equal for all k.

and c probably shows something similar. I will have to write it out in a bit in Maple.

Thanks!
 

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