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September 24th, 2012, 12:47 PM  #1 
Newbie Joined: Aug 2012 Posts: 16 Thanks: 0  Rational expression constants
Find, Algebraically, the constants A and B such that 7x6 / x^2x6 = A/x+2 + B/x3

September 24th, 2012, 01:20 PM  #2 
Global Moderator Joined: Oct 2008 From: London, Ontario, Canada  The Forest City Posts: 7,958 Thanks: 1146 Math Focus: Elementary mathematics and beyond  Re: Rational expression constants
Will you post your attempt and/or any ideas you have?

September 24th, 2012, 01:43 PM  #3 
Newbie Joined: Aug 2012 Posts: 16 Thanks: 0  Re: Rational expression constants
yea sure, here they are: ive tried using (x+2)(x3) as the denominator and took it out from all 3 then, ax + 3a + bx + 2b = 7x6 ive tried substituting a and couldnt go any further than this 
September 24th, 2012, 01:47 PM  #4 
Global Moderator Joined: Oct 2008 From: London, Ontario, Canada  The Forest City Posts: 7,958 Thanks: 1146 Math Focus: Elementary mathematics and beyond  Re: Rational expression constants Now set x = 3 and you get B = 3. Do you see how? 
September 24th, 2012, 02:11 PM  #5 
Newbie Joined: Aug 2012 Posts: 16 Thanks: 0  Re: Rational expression constants
I've tried following your suggestions but couldn't quite get the 3 for B, however what I got was 7x6 = B by eliminating all the like factors and can you also elaborate on the rules of plugging in the 3 as x. Thanks

September 24th, 2012, 02:14 PM  #6 
Global Moderator Joined: Oct 2008 From: London, Ontario, Canada  The Forest City Posts: 7,958 Thanks: 1146 Math Focus: Elementary mathematics and beyond  Re: Rational expression constants 
September 24th, 2012, 02:18 PM  #7 
Newbie Joined: Aug 2012 Posts: 16 Thanks: 0  Re: Rational expression constants
alright I see, I just made a small error and forgot to put 5 infront of B. Anyways, thanks for clearing this up.


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