Is Divisibility Sufficient for Proving a Product Divides Another Product?

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SUMMARY

The discussion centers on proving that if \( a \) divides \( c \) and \( b \) divides \( c \), with \( (a, b) = d \), then \( ab \) divides \( cd \). The proof utilizes the definitions of divisibility, expressing \( c \) as \( c = am \) and \( c = bn \), leading to \( d = an + bm \). By substituting these expressions into \( cd \), it is established that \( ab \) indeed divides \( cd \) through the relationship \( cd = c(an + bm) \).

PREREQUISITES
  • Understanding of basic number theory concepts such as divisibility.
  • Familiarity with the notation and properties of greatest common divisors (GCD).
  • Knowledge of algebraic manipulation and substitution techniques.
  • Basic experience with proofs in mathematics, particularly in abstract algebra.
NEXT STEPS
  • Study the properties of divisibility in number theory.
  • Learn about the Euclidean algorithm for finding the greatest common divisor.
  • Explore algebraic proofs involving divisibility and GCD.
  • Investigate applications of divisibility in modular arithmetic.
USEFUL FOR

Students of mathematics, particularly those studying number theory, algebra, or preparing for advanced proofs in discrete mathematics.

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Homework Statement


Show that if a | c and b | c, and (a, b) = d, then ab | cd.

Homework Equations


The Attempt at a Solution


Abstract divisibility.
We have c=am, c=bn, and d=an+bm.
 
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Could I multiply d=an+bm by c.
Then I have cd=acn+bcm
We have cd=c(an+bm)
cd=cd
Thus, ab | cd
 

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