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LCM equation (Posted on 2013-11-19) Difficulty: 2 of 5
The least common multiple (LCM) of 2 numbers is the smallest number that they both divide evenly into.
e.g.:
LCM(8,10)=40
LCM(17,11)=187

For any integer n, show that LCM(9n + 8, 6n + 5) = 54n^2 + 93n + 40.

No Solution Yet Submitted by Ady TZIDON    
Rating: 4.0000 (2 votes)

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Solution Another Proof | Comment 2 of 5 |
Any common factor of (9n + 8) and (6n + 5) is also a factor of their difference, (3n + 3).

Any common factor of (9n + 8), (6n + 5) and (3n + 3) is also a factor of (6n + 5) - (3n + 3), i.e. (3n + 2).

Any common factor of  (9n + 8), (6n + 5), (3n + 3) and (3n + 2) is also a factor of (3n + 3) - (3n + 2), i.e. 1.  

But the only factor of 1 is 1, so, all of the terms mentioned are relatively prime, including (9n + 8) and (6n + 5).

Edited on November 20, 2013, 9:11 am
  Posted by Steve Herman on 2013-11-19 19:31:04

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