Adding and subtracting Rational Expressions

AI Thread Summary
The discussion focuses on resolving mistakes in adding and subtracting rational expressions. One participant points out an error in the calculation of a combined expression, highlighting that the provided answer does not hold true for specific values of x. There is also a suggestion to improve the formatting of the fraction bar for clarity. The conversation emphasizes the importance of accuracy in mathematical expressions and notation. Overall, the participants are seeking to clarify their understanding of rational expressions and correct any miscalculations.
caprija
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I'm stuck on how to do this problem

My attempt:


Me.jpg




the answer to the second one is 3x + 2/(x+2)(x-2)

Can someone point out my mistake?
 
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When you said that:

\frac{2}{x(x+2)} + \frac{x}{x(x-2)} = \frac{x^2-4}{(x+2))(x-2)}

That is incorrect (take x = 1 and you get -1/3 = 1).

Also, just as a style note: you should write the fraction bar so that it extends over both the top and the bottom. (does that make sense?) For example, on your last line, you have a little bar below the 4, you should instead have a bar going from the start of the first 2x to the end of the last 2x. Unless of course you meant to write:
2x - \frac{4}{(x+2)(x-2)} + x^2 + 2x

edit... also the "answer" you wrote is not correct.
 
Last edited:
Alright, Thank you.
 
I tried to combine those 2 formulas but it didn't work. I tried using another case where there are 2 red balls and 2 blue balls only so when combining the formula I got ##\frac{(4-1)!}{2!2!}=\frac{3}{2}## which does not make sense. Is there any formula to calculate cyclic permutation of identical objects or I have to do it by listing all the possibilities? Thanks
Since ##px^9+q## is the factor, then ##x^9=\frac{-q}{p}## will be one of the roots. Let ##f(x)=27x^{18}+bx^9+70##, then: $$27\left(\frac{-q}{p}\right)^2+b\left(\frac{-q}{p}\right)+70=0$$ $$b=27 \frac{q}{p}+70 \frac{p}{q}$$ $$b=\frac{27q^2+70p^2}{pq}$$ From this expression, it looks like there is no greatest value of ##b## because increasing the value of ##p## and ##q## will also increase the value of ##b##. How to find the greatest value of ##b##? Thanks
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