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 January 26th, 2012, 08:58 AM #1 Member   Joined: Dec 2011 Posts: 44 Thanks: 0 Adding/Subtracting Rational Expression (answer check) Here's the problem: 7x/x+1 + 8/x-1 - 14/x^2-1 I'm getting 7x^2-x-6/(x+1)(x-1) and after factoring the numerator and simplifying, I end up with 7x+6/(x+1) is this right?
January 26th, 2012, 11:43 AM   #2
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 Originally Posted by boomer029 Here's the problem: 7x/x+1 + 8/x-1 - 14/x^2-1 I'm getting 7x^2-x-6/(x+1)(x-1) and after factoring the numerator and simplifying, I end up with 7x+6/(x+1) is this right?
Hi boomer029,

You made a slight error with the sign of your second term. Go back and redo your first step. I think you'll find it to be ${\frac{7x^2+x-6}{(x+1)(x-1)}$.

 January 26th, 2012, 11:51 AM #3 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: Adding/Subtracting Rational Expression (answer check) $\frac{7x}{x+1}+\frac{8}{x-1}-\frac{14}{x^2-1}=\frac{7x(x-1)+8(x+1)-14}{(x+1)(x-1)}=\frac{7x^2-7x+8x+8-14}{(x+1)(x-1)}=$ $\frac{7x^2+x-6}{(x+1)(x-1)}=\frac{(x+1)(7x-6)}{(x+1)(x-1)}=\frac{7x-6}{x-1}$

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