We find the lowest common denominator by factoring each of these denominators
first. The first denominator will have factors of x plus 2 times x minus 6,
since factors of 12 that sum to negative 4 are positive 2 and negative 6. The
factors for x squared minus 36 would be x minus 6 and x plus 6. This is just the
difference of two perfect squares. We can see that both of the denominators
share a common factor of x minus 6. So this is the factor they share, and we
list it in the middle. The other factor of this denominator is x plus 2, and the
other factor of this denominator is x plus 6. Finally, we just multiply all
these factors together to get our lowest common denominator, right here.