The least common multiple (LCM) of two numbers is the smallest number that is a multiple of both numbers. In this case, the LCM of ab and bc would be the product of the two numbers divided by their greatest common divisor (GCD), which is b. Therefore, the LCM of ab and bc is abc.
The GCF is b.
LCM is the multiple of the highest power of prime factors in two or more numbers. Example: LCM of 9, 15, and 25 is 225, which is the multiple of the highest power of prime factors in 9, 15, and 25 (32 x 52).
bcd
The GCF is b.
That factors to (b + 3)(a + c)