Definition of a Restriction in Linear Algebra

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SUMMARY

The discussion centers on the concept of a restriction in linear algebra, specifically in the context of linear transformations S and T from a finite-dimensional vector space V to itself. The key takeaway is that the restriction of a linear transformation S to a subspace W, which is the image of another transformation T, creates a new mapping R: W→V. This mapping is defined such that for every vector x in W, R(x) equals S(x). The inequality n(ST) ≤ n(S) + n(T) is also highlighted, indicating a relationship between the ranks of the transformations.

PREREQUISITES
  • Understanding of finite-dimensional vector spaces
  • Familiarity with linear transformations and their properties
  • Knowledge of the concept of image and kernel in linear algebra
  • Basic grasp of rank-nullity theorem
NEXT STEPS
  • Study the definition and properties of linear transformations in detail
  • Learn about the rank and nullity of linear transformations
  • Explore the concept of image and kernel in linear algebra
  • Investigate the implications of the rank-nullity theorem on linear mappings
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Students of linear algebra, educators teaching vector spaces and transformations, and anyone seeking to deepen their understanding of linear mappings and their restrictions.

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Homework Statement


Let V be a finite-dimensional vector over ℝ, and let S and T be linear transformations from V to V

Show that n(ST)≤n(S)+n(T)


Given Hints
Consider the restriction of S to W where W=im(T)


Can someone please tell me what the above hint means?

I haven't attempted a solution, but then I'm not asking for a hint for the solution. I just require the definition of a restriction please! I haven't been able to find a definition of one in my lecture notes. They are just mentioned.

Thanks!
 
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The restriction simply means you're restricting the domain of S to those vectors in V which are elements of W. In other words, you have a new mapping R: W→V where x maps to S(x) for all x∈W.
 

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