1) In order for you to know the LCM of a monomial (a number with a variable) and a constant you can just simply get the factors.
When you are asked to get
the LCM of let’s say 12 and 24, we would quickly know that it is 24. But what
should you do to get the LCM of for example, 6x and 3?
We first get the factors of each term:
6x = 2 * 3 * x
3 = 3
So the LCM would be combining all the factors, getting the highest exponent of the bases seen, so the LCM is 2 * 3 * x = 6x.
2) We need to get the factors of each binomial, we get the GCF of the terms in each binomial. To get the GCF it is similar to getting the LCM except that you get the common factors.
In order to get the LCM of the binomial we factor each.
First, factor 5x -20
5x = 5 * x
20 = 5 * 2²
GCF = 5
5x - 20 = 5(x - 4)
x - 4 = x - 4
LCM = 5 * (x - 4) = 5x - 20
3) You need to have the same denominator before adding the numerators. Simplify each fraction if possible.