# Math Help - Rational Expressions

1. ## Rational Expressions

What would be the common denominator for these three demoninators
2x, 4, 2x+3

thanks so much....would it just be to multiply all three by each other?

2. Originally Posted by Natalie
What would be the common denominator for these three demoninators
2x, 4, 2x+3

thanks so much....would it just be to multiply all three by each other?
multiplying each other would be one way to do it, but it's a slight overkill.

4x(2x + 3) would do it, as oppsed to the 8x(2x + 3) you would get if you multiply all three. it's no big deal though, if you use 8x(2x + 3) the extra 2 would eventually cancal out, and maybe more

3. oooh great thanks so much, that helps.

so is there any faster ways in simplifying this?

4x
---------
(x+5)(x-1)

subract

5
---
4

thanks again

4. Originally Posted by Natalie
oooh great thanks so much, that helps.

so is there any faster ways in simplifying this?

4x
---------
(x+5)(x-1)

subract

5
---
4

thanks again

..........4x .........................5
...------------.....-..........-----
....(x+5)(x-1).....................4

...........8x...-...5(x + 5)(x - 1)
..= ..-------------------------
.............4(x + 5)(x - 1)

...........8x...-...5(x^2 + 4x - 5)
..= ..---------------------------
.............4(x + 5)(x - 1)

...........8x...-...(5x^2 + 20x - 25)
..= ..---------------------------
...............4(x + 5)(x - 1)

............-5x^2 -12x + 25
..= ..---------------------------
...............4(x + 5)(x - 1)