LCD of 1 over 5x and -9 over x^2 + 4x?

Answer 1

The two denominators are 5x and (x^2 +4x).
We can factor x^2 + 4x into x(x+4).
The lowest common denominator will be 5x(x+4).
You must take one of everything.
Answer: LCD = 5x(x+4)

Answer 2

Okay, 1/5x and -9/(x^2 + 4x) both can be factorized as follows: 1/x(1/5) and 1/x(-9/(x+4)). Hence, since these cannot be factorized any further, we know trhat 1/x is the LCD