How do you find the LCD of 3x and 9x^2?

Question

mathmale · Answer

Are you in a situation where you have two fractions, one of which has denominator 3x and the other 9x^2?

    A             B
------ - -------
  3x           9x^2

If so, you need to determine which factors 3x and 9x^2 have in common.  Can 9x^2 be divided by 3x?  Yes.  So, your denominators are 3x and 3x(3x).
The 2nd one, 3x3x, or 9x^2, is your LCD.

Mult. A and 3x by 3x to obtain a fraction with the LCD in it that is equivalent to A/(3x).

dsena · Answer

Okay, thanks! The second denominator was 9x^2y actually. Would the LCD be 9x^2y?

mathmale · Answer

Yes, it would.  If you want further feedback, please share your work here.

dsena · Answer

Okay, thank you for the help!

mathmale · Answer

You're welcome!

dsena · Answer

So I'm being asked to fill in the blank to make an equivalent fraction with the given denominator. $$\frac{ 5 }{ 3x}=\frac{ ? }{ 9x^2y }$$

dsena · Answer

Would I multiply the 9x^2y by 5?

danjs · Answer

you want the fraction on the right to be the same as the one on the left...

danjs · Answer

you see the denominator was multiplied by 3*x*y  to get to the right fraction. To keep it equals the same,  you have to do the same to the numerator

danjs · Answer

$$\large \frac{ 5 }{ 3x }*\frac{ 3xy }{ 3xy }=$$