Proving the Equality of Fractions Using Multiplicative Properties

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SUMMARY

The discussion centers on proving the equality of fractions, specifically that a/b = c/d if and only if ad = bc. The proof utilizes the multiplicative inverse property, commutativity, associativity, and transitivity. The key steps involve multiplying both sides of the equation by bd, leading to the conclusion that ad = bc. The discussion also emphasizes the necessity of proving both directions of the equivalence, confirming that if ad = bc, then a/b = c/d.

PREREQUISITES
  • Understanding of basic algebraic properties: multiplicative inverse, commutativity, associativity, and transitivity.
  • Familiarity with fractions and their manipulation.
  • Knowledge of proof techniques in mathematics.
  • Ability to perform algebraic operations involving variables.
NEXT STEPS
  • Study the properties of fractions in depth, focusing on the multiplicative inverse property.
  • Learn about algebraic proof techniques, including direct proof and proof by contradiction.
  • Explore examples of proving equivalences in algebra, particularly involving fractions.
  • Investigate the implications of the commutative and associative properties in algebraic expressions.
USEFUL FOR

This discussion is beneficial for students learning algebra, mathematics educators teaching proof techniques, and anyone interested in understanding the foundational properties of fractions and their equivalences.

koshn
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Homework Statement


Prove that a/b=c/d if and only if ad=bc

Homework Equations



Multiplicative inverse property: (a)(a^1) = 1
Commutativity: ab = ba
Associativity: (ab)c = a(bc)
Transitivity: If a = b and b = c then a = c

The Attempt at a Solution



a/b=c/d=ab^1= cd^1. Multiplying both sides by (b)(d) I get, (a)(b^1)(b)(d) = (c)(d^1)(d)(b). Using the multiplicative inverse property, I get that ad=cb. And this is where I'm stuck. I don't know if this was the point of the proof. I'm not sure if the point was to prove (a/b)=(c/d)=ad=ac or if there is some other way to go about this.
 
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You've proven that ad=bc if a/b=c/d. Now you need to prove the other direction, namely start with ad=bc and show that a/b=c/d.
 
Ok that makes sense. Thanks.
 

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