Steve G.

asked • 06/11/14

Rational Expressions addition and subtraction

(4/x+1)+(1/x^2-x+1)-(12/x^3+1)

1 Expert Answer

By:

Javier H. answered • 06/11/14

Tutor
New to Wyzant

I can tell jokes!?!? but also really want to help!

Steve G.

you didn't answer it, you simply rearranged the order. i have the answer I just can't figure out how to get to the answer
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06/11/14

Philip P.

tutor
If you factor the denominators, the expression becomes:
 
   4               1                   12
------  +  ------------  -  ---------------
(x+1)     (x+1)(x-1)     (x+1)2(x-1)
 
Put the terms over a common denominator, which will be (x+1)2(x-1).  Then add and subtract the numerators and simplify.
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06/11/14

Steve G.

The second fraction you have is incorrect. if foiled that would give me x^2-1 not x^2-x+1
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06/11/14

Philip P.

tutor
You are right!  It should be:
 
    4              1                  12
-------  +  ----------  -  -----------------
(x+1)      (x2-x+1)      (x+1)(x2-x+1)
 
Common denominator is (x+1)(x2-x+1)
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06/11/14

Steve G.

Thank you! I am still having trouble with it though. The book is saying the answer is 4x-7. I keep getting 4x^2-15x-7
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06/12/14

Philip P.

tutor
When you put it over the common denominator, you get:
 
   4x2-3x-7              (x+1)(4x-7)             4x-7
-----------------  =   ------------------  =  ------------
(x+1)(x2-x+1)       (x+1)(x2-x+1)       (x2-x+1)
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06/12/14

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