Find out if it's linear transformation

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Homework Help Overview

The discussion revolves around the existence of a linear transformation from \(\mathbb{R}^2\) to \(\mathbb{R}^2\) given specific mappings of two vectors. Participants are examining the conditions that define linear transformations and whether the provided mappings satisfy these conditions.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants explore the necessary conditions for a linear transformation, specifically the additivity and homogeneity properties. There is an attempt to verify these properties using the given vectors and their images under the transformation.

Discussion Status

Some participants have identified a potential relationship between the two vectors being acted upon by the transformation, leading to a consideration of scalar multiplication. There is a suggestion that this relationship may indicate the non-existence of the linear transformation, but no consensus has been reached.

Contextual Notes

Participants are working under the assumption that the mappings provided are the only information available to determine the existence of the linear transformation. There is an emphasis on verifying the conditions for linearity without additional context or information.

Kernul
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Homework Statement


Does a linear transformation ##g : \mathbb{R}^2 \rightarrow \mathbb{R}^2## so that ##g((2, -3)) = (5, -4)## and ##g((-\frac{1}{2}, \frac{3}{4})) = (0, 2)## exist?

Homework Equations

The Attempt at a Solution


For a linear transformation to exist we need to know if those two satisfy the following conditions:
##g(\vec v_1 + \vec v_2) = g(\vec v_1) + g(\vec v_2)## for any ##\vec v_1, \vec v_2## in ##\mathbb{R}^2##
##g(\alpha \vec v) = \alpha g(\vec v)## for any scalar ##\alpha##
So I thought I should do like this:
I sum the two vectors ##(2, -3)## and ##(-\frac{1}{2}, \frac{3}{4})## like this ##g((2, -3) + (-\frac{1}{2}, \frac{3}{4}))## and put it equal to the sum of ##(5, -4)## and ##(0, 2)##. I will then have something like this:
##g((2, -3) + (-\frac{1}{2}, \frac{3}{4})) = (5, -4) + (0, 2)##
##g((\frac{3}{2}, -\frac{9}{4})) = (5, -2)##
But at this point I actually don't know if it really exist or not. Am I missing something?
 
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Kernul said:

Homework Statement


Does a linear transformation ##g : \mathbb{R}^2 \rightarrow \mathbb{R}^2## so that ##g((2, -3)) = (5, -4)## and ##g((-\frac{1}{2}, \frac{3}{4})) = (0, 2)## exist?

Am I missing something?

Do you notice anything about the two vectors being acted on by ##g##?
 
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PeroK said:
Do you notice anything about the two vectors being acted on by ##g##?
Oh! If I multiply by ##-4## the second vector acted on by ##g##, I'll get the first vector! But I have to multiply the vector that is is equal to by ##-4## too. And since ##(0, -8)## is not equal to ##(5, -4)## means that the linear transformation doesn't exist, right?
 
Kernul said:
Oh! If I multiply by ##-4## the second vector acted on by ##g##, I'll get the first vector! But I have to multiply the vector that is is equal to by ##-4## too. And since ##(0, -8)## is not equal to ##(5, -4)## means that the linear transformation doesn't exist, right?

Exactly.
 
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