# Adding and Subtracting Algebraic Fractions

• Oct 6th 2012, 02:11 AM
jeremyjezzanba
Hi how do you solve these two questions? Simplify the following:

(both attached)

Thanks.
• Oct 6th 2012, 04:54 AM
chiro
Re: Adding and Subtracting Algebraic Fractions
Hey jeremyjezzanba.

You can't really solve these equations since there is nothing to compare them to: comparisons need either an inequality (like > or <) or an equality (i.e. = ).

You just have an expression which means nothing: if you make it equal to something or give it an inequality then this is a different thing but as it stands you can't solve anything.

You can simplify these but that's different: simplifying fractions of A/B + C/D is basically using the rule [AD+BC]/BD. Have you covered this in class before?
• Oct 6th 2012, 05:26 AM
jeremyjezzanba
Re: Adding and Subtracting Algebraic Fractions
yeh sorry i didn't mean solve i meant simplify. We have very briefly but it is a broad topic so this exact part hasn't been covered. If i could just get a worked example of them i would be able to work others out, thanks.
• Oct 6th 2012, 05:34 AM
chiro
Re: Adding and Subtracting Algebraic Fractions
So for the first one you have 1/(x-5) - 3/(x+4) = [x+4 - 3(x-5)]/[(x+4)(x-5)] = (19 - 2x)/[(x-4)(x-5)]

Edited: For typo
• Oct 6th 2012, 04:42 PM
jeremyjezzanba
Re: Adding and Subtracting Algebraic Fractions
thankyou but it is X+4 and it is not the right answer
• Oct 6th 2012, 05:11 PM
skeeter
Re: Adding and Subtracting Algebraic Fractions
Quote:

Originally Posted by jeremyjezzanba
thankyou but it is X+4 and it is not the right answer

chiro made a typo, but you should be able to take what was provided, change x-4 to x+4 and combine the fractions yourself
• Oct 6th 2012, 05:15 PM
jeremyjezzanba
Re: Adding and Subtracting Algebraic Fractions
yes thanks I got it in the end but Still can't work out the second question
• Oct 6th 2012, 05:31 PM
skeeter
Re: Adding and Subtracting Algebraic Fractions
note that x-2 = -(2-x)
• Oct 6th 2012, 05:37 PM
jeremyjezzanba
Re: Adding and Subtracting Algebraic Fractions
I understand that I just don't get the method
• Oct 6th 2012, 05:44 PM
skeeter
Re: Adding and Subtracting Algebraic Fractions
$\displaystyle \frac{3}{x-2} + \frac{4}{2-x} = \frac{3}{x-2} + \frac{-4}{-(2-x)}$
• Oct 6th 2012, 05:51 PM
jeremyjezzanba
Re: Adding and Subtracting Algebraic Fractions
Attachment 25086

is this correct?
• Oct 6th 2012, 05:56 PM
skeeter
Re: Adding and Subtracting Algebraic Fractions
no.

$\displaystyle \frac{3}{x-2} + \frac{4}{2-x} = \frac{3}{x-2} + \frac{-4}{-(2-x)} = \frac{3}{x-2} + \frac{-4}{x-2} = \frac{3-4}{x-2} = \frac{-1}{x-2}$