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Precalculus 21 Online
OpenStudy (anonymous):

Can someone help me simplify complex rational expressions?

OpenStudy (anonymous):

Can you give an example of what you're working on?

OpenStudy (anonymous):

Simplify ((1/x) + (1/y)) / (x+y)

OpenStudy (anonymous):

Notice that your adding x to y in two different places (in different forms) and try to find a way to get them to cancel. Multiply your 1/x by y/y and your 1/y by x/x. ( you. can do this because y/y = 1 and multiply by 1 doesn't change anything.) now add those two fractions together now that they have the same common denominator. Next, remember that x + y (on the bottom of your original fraction) is actually over 1. Now you have one fraction divided by another. To do that, flip over the bottom one and multiply. Your x + y will cancel and you'll be left with 1/xy

OpenStudy (anonymous):

okay that helped for that one but how would i do harder ones like ((x/3) - 1) / (x-3)

OpenStudy (anonymous):

That problem is actually very similar. Start by Turning 1 into 3/3 and getting so you have 2 fractions on the top with a common denominator that you can add into one fraction

OpenStudy (anonymous):

so it would then be ((x-3/3)) / x-3 ?

OpenStudy (anonymous):

Perfect! Now take the bottom of your whole fraction and remember that it has a silent 1 under it, so you really have [(x-3)/3]/[(x-3)/1] then take flip your bottom fraction and multiply by your top

OpenStudy (anonymous):

so the x-3's would cross out leaving me 1/3?

OpenStudy (anonymous):

You got it! : )

OpenStudy (anonymous):

Thank you so much! I have a couple more problems if you could help me but if you don't want to or your'e busy then that's fine.

OpenStudy (anonymous):

I'm here. What you got?

OpenStudy (anonymous):

((1+ 1/x)) / ((3- 1/x))

OpenStudy (anonymous):

Stat by turning both of your whole numbers into fractions, getting common denominators, and adding.

OpenStudy (anonymous):

1 will equal x/x and 3 will be 9/3

OpenStudy (anonymous):

Oops typo

OpenStudy (anonymous):

3 will be 3x/x

OpenStudy (anonymous):

so the answer is x/4x?

OpenStudy (anonymous):

Not what I got, did you have [(x+1)/x]/[(3x-1)/x]?

OpenStudy (anonymous):

I might have thrown you off with that mistake I made up there

OpenStudy (anonymous):

after I get that I do the flip over and multiple thing?

OpenStudy (anonymous):

Yup, don't try to simplify too much. The x's will cancel, but the x+1 and the 3x-1 will not

OpenStudy (anonymous):

so it's x+1/3x-1?

OpenStudy (anonymous):

On the nose! : )

OpenStudy (anonymous):

awesome :) so I started a different problem and got to the flip and multiple part. I got (1/x+1) times ((x-3)(x+1)+(x-3))/1 and I crossed out the x+1's

OpenStudy (anonymous):

You still there?

OpenStudy (anonymous):

Oops sorry stepped out for a bit

OpenStudy (anonymous):

That looks a little complicated. What was the starting problem?

OpenStudy (anonymous):

(1/(x+1)) / (1/(x^2-2x-3)) + (1/x-3))

OpenStudy (anonymous):

Is that last part 1/(x+3) or (1/x) + 3

OpenStudy (anonymous):

Except its a minus, this is kinda hard on an ipad

OpenStudy (anonymous):

1/(x+3)

OpenStudy (anonymous):

Ok, very sorry, my Internet died, but I figured it out

OpenStudy (anonymous):

You were exactly right when you factored. Then you need to get a common denomination on those two fractions on the bottom of your big fraction. Since you already factored you can see that all you need to do is multiply (x+1)/(x+1) times your 1/(x-3)

OpenStudy (anonymous):

okay and I have one more but I need to go eat dinner so if you could just kind of give a brief description on how to do it and if you're on when I'm done I can ask questions if I need to. (x-(x/x+3)) / x+2

OpenStudy (anonymous):

Ok I did it but it' s not quick to explain one. I'll type it up, and if you have to leave before I'm done that's ok

OpenStudy (anonymous):

okay. Thank you so much for all your help. I really appreciate it

OpenStudy (anonymous):

First multiply your x by (x+3)/(x+3)

OpenStudy (anonymous):

Then multiply your x(x+3) out so you have x^2 + 3x

OpenStudy (anonymous):

Now, when you add those fractions with the common denominator (x+3) you'll end up with x^2 + 3x -x

OpenStudy (anonymous):

That simplifies to x^2 + 2x

OpenStudy (anonymous):

Now you need to re factor it so you have x(x+2)

OpenStudy (anonymous):

So you'll have [(x(x+2))/(x+3)]/[(x+2)/1]

OpenStudy (anonymous):

When you flip and multiply your (x+2) will cancel and you'll be left with x/(x+3)

OpenStudy (anonymous):

It was fun working with you. Good luck!

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