Originally Posted by

**harkapobi** Hi, I need some help proving that the below formula is true.

It says: Use the Fundamental Theorem of Arithmetic to prove the following formula connecting GCD and LCM for three integers.

[*a, b, c*] = *abc*(*a, b, c*) / (*b, c*)(*c, a*)(*a, b*)

Now I know that FTA says that any integer has a unique decomposition of primes. And I know you can write any two integers as a decomposition of the same primes, with some powers that possibly equal 0.

How can I use this to prove the formula? Please help.

Katy.