- #1
scottstapp
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Homework Statement
If a and b are positive integers, then ab=gcd(a,b)*lcm(a,b).
Homework Equations
I am allowed to use the following propositions which have already been proved:
(1) If d is a common divisor of a and b, then ab/d is a common multiple of a and b.
(2) If m is a common multiple of a and b and m divides ab, then ab/m is a common divisor of a and b.
A hint given:
set d=gcd(a,b) and m=lcm(a,b). Use (1) to show that ab/d>=m. Use (2) to show that ab/m<=d.
The Attempt at a Solution
1. Let a and b be positive integers. Suppose d=gcd(a,b) and m=lcm(a,b).
2. By (1) ab/d is a common multiple of a and b so ab/d=aL and ab/d=bK
3. Multiply by m gives mab/d=aLm and mab/d=bKm
4. ab/d>=m
I am missing a step between 2 and 3. Any suggestions?
Thanks,
Scott