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 September 17th, 2010, 04:02 PM #1 Newbie   Joined: Sep 2010 Posts: 4 Thanks: 0 Dividing Rational Expression Problem I used to be pretty good at solving rational expressions, but this problem has triggered some sort of brain fart for me. I took a simple review test recently that spanned years worth of math, and I stumbled upon a rational expression division problem that is messing with my head. Here's the problem I already know that I multiply using the reciprocal, so I'll just type it out with that already done. y - 3???3y + 6 ----- * --------- y + 2???6 - y^2 I figure right off the bat I eliminate the 6's and the y's, but then I am left with -3 over 2 multiplied by 3y over -y^2. I know the answer is 3- over 2, but I am having a hard time figuring out how I get from where I left off to the answer. September 17th, 2010, 04:11 PM #2 Senior Member   Joined: Jul 2010 From: St. Augustine, FL., U.S.A.'s oldest city Posts: 12,211 Thanks: 521 Math Focus: Calculus/ODEs Re: Dividing Rational Expression Problem You can't eliminate the 6's and y's like that, only factors can be divided out, or eliminated, not addends. (x + 3)/(y + 3) ? x/y (3x)/(3y) = x/y You can factor the 3y + 6 as 3(y + 2) and eliminate y + 2 that is a factor in both the numerator and denominator. September 17th, 2010, 04:27 PM #3 Newbie   Joined: Sep 2010 Posts: 4 Thanks: 0 Re: Dividing Rational Expression Problem Okay, makes more sense. With the 6 - y^2 though, what do I do there? September 17th, 2010, 04:34 PM #4 Senior Member   Joined: Jul 2010 From: St. Augustine, FL., U.S.A.'s oldest city Posts: 12,211 Thanks: 521 Math Focus: Calculus/ODEs Re: Dividing Rational Expression Problem If that were 9 - y�, you could factor it as a difference of squares as (3 + y)(3 - y) = -(y + 3)(y - 3), but it is not. 6 - y� can be factored as [?(6) + y][?(6) - y], but neither factor is in the numerator, so I would leave it as [3(y - 3)]/(6 - y�) What result are you expected to obtain? September 17th, 2010, 04:39 PM   #5
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Re: Dividing Rational Expression Problem

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 Originally Posted by MarkFL If that were 9 - y�, you could factor it as a difference of squares as (3 + y)(3 - y) = -(y + 3)(y - 3), but it is not. 6 - y� can be factored as [?(6) + y][?(6) - y], but neither factor is in the numerator, so I would leave it as [3(y - 3)]/(6 - y�) What result are you expected to obtain?
This is a practice test I am taking for review of all my high-school math before I hit the SATs. It is a multi-choice question. I am supposed to find what the expression is equivalent to out of the 4 answers; basically simplify it as much as possible. I ended up blanking entirely on the question. The answer ended up being -3/2. Does that help more? September 17th, 2010, 04:42 PM #6 Senior Member   Joined: Jul 2010 From: St. Augustine, FL., U.S.A.'s oldest city Posts: 12,211 Thanks: 521 Math Focus: Calculus/ODEs Re: Dividing Rational Expression Problem Are you sure the y^2 in the denominator isn't 2y? That would enable simplification to -3/2. September 17th, 2010, 04:47 PM   #7
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Re: Dividing Rational Expression Problem

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 Originally Posted by MarkFL Are you sure the y^2 in the denominator isn't 2y? That would enable simplification to -3/2.
Oh man... Thanks a ton for helping me out. Yeesh, I'm fuzzy enough on this stuff as it is. The last thing I need to be doing is incorrectly writing out the equations. Once again, big thanks. September 17th, 2010, 04:53 PM #8 Senior Member   Joined: Jul 2010 From: St. Augustine, FL., U.S.A.'s oldest city Posts: 12,211 Thanks: 521 Math Focus: Calculus/ODEs Re: Dividing Rational Expression Problem No problem, my friend!  Tags dividing, expression, problem, rational Thread Tools Show Printable Version Email this Page Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Similar Threads Thread Thread Starter Forum Replies Last Post guru123 Algebra 2 September 5th, 2013 07:02 PM AKofTroy Algebra 6 July 13th, 2013 04:19 PM lyahnke1 Elementary Math 2 April 15th, 2013 08:33 PM lalex0710 Algebra 5 September 23rd, 2012 03:17 PM dudeman893 Algebra 10 September 5th, 2010 07:43 AM

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