What's the LMC of - 1 and 3

The prime factor (s) of 3 are:

1 x 3

The prime factor (s) of - 1 are:

-1 * - 1

Merging them together using the least amount of factors, you get:

-1 x 3

Then you can multiply those numbers together to get the Least Common Multiple (LCM) of 3 and - 1 as follows:

-3