The least common multiple is the smallest expression that can be divided by both of the given expressions.
x^2 - 16 = (x - 4)(x + 4)
x^2 + 4x - 32 = (x + 8)(x - 4)
Both of the factored versions of the expressions have an (x - 4) in them. Thus, that will automatically be included in the LCM. Next, we have to include the (x + 4) and the (x + 8) in our LCM.
LCM = (x - 4)(x + 4)(x + 8)
Hope this helps! :)