Question 22839
Is this a complex fraction that looks like this:
{{{((x^2-4)/(x^2-4x-21))/((x^2-7x+10)/(x^2-2x-35))}}}


If so, then notice that you have a numerator which is a fraction and a denominator which is a fraction.  Notice also that the middle fraction line separating the numerator and the denominator is the longest line.  Now, just "unstack" the problem by writing this in the form of a 
(NUMERATOR) divided by (DENOMINATOR).  

{{{ (x^2-4)/(x^2-4x-21)}}} {{{divided by}}} {{{ (x^2-7x+10)/(x^2-2x-35)}}}

Now, invert the second fraction and multiply.  While you are at it, factor all the trinomials:
{{{(((x-2)*(x+2))/((x-7)(x+3)))*(((x-7)*(x+5))/((x-5)*(x-2)))}}}


Divide out the (x-7) and the (x-2) factors, and you should be left with {{{((x+2)*(x+5))/((x+3)*(x-5))}}} for your final answer.


R^2 at SCC