Question

LCD? 1/45ab^2 and 5a/18b

Answer 1

factor both denominators:
45ab^2 = 3 x 3 x 5 x a x b x b
18b = 3 x 3 x 2 x b
So, drop down all common factors (3 x 3 x b), and find whatever remaining factors there are (5 x a x b x 2). So your answer is 3 x 3 x 5 x 2 x a x b x b, or 90ab^2