Checking if Rationals are Closed Under Addition and Scalar Multiplication

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SUMMARY

The discussion centers on the closure properties of the vector space of rational numbers under addition and scalar multiplication. It is established that the set of rational numbers is closed under addition, as adding two rational numbers (e.g., 1/2 + 1/2) results in another rational number (2). However, the set fails to be closed under scalar multiplication when the scalar is an integer, as multiplying a rational number by an integer can yield an integer, which is still a rational number but does not remain within the confines of the vector space defined by rational numbers alone.

PREREQUISITES
  • Understanding of vector spaces and their properties
  • Knowledge of rational numbers and their operations
  • Familiarity with scalar multiplication concepts
  • Basic algebraic manipulation skills
NEXT STEPS
  • Study the properties of vector spaces in linear algebra
  • Research closure properties of different number sets
  • Explore scalar multiplication in various vector spaces
  • Examine examples of vector spaces that include integers and rationals
USEFUL FOR

Students of linear algebra, mathematics educators, and anyone interested in the properties of vector spaces and rational numbers.

robierob12
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Homework Statement



Check to see if the (vector space) set of rational numbers is closed under addition and scalar multiplication

Homework Equations



The book says this holds for addition but fails for scalar multiplication.

The Attempt at a Solution



Im a little confused. You can add two of the same rational number like (1/2) and (1/2) and get an integer. Now your out of the vector space. Where is my logic failing me?
 
Physics news on Phys.org
Integers are rationals: 2 = 2/1 = 4/2 = ...
 
it's always the obvious. how funny
 

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