LCM of (2+9u),(4-81u^2)and (2-9u)

Answer 1

LOL

a^2 - b^2 = (a-b)(a+b) identity, know it

so
4 - 81 u^2 = (2-9u)(2+9u)

so
4 - 81 u^2 is the multiple you are looking for