Question 127154
{{{6/(z-5) + 6/(z+5)}}} 


You need a common denominator.  Since the two denominators have no factors in common, the lowest common denominator is simply the product of the two.  {{{(z-5)(z+5)=z^2-25}}}  (Remember the factorization of the difference of two squares)


So:
{{{(6(z+5)+6(z-5))/(z^2-25)}}}


{{{(6z+30+6z-30)/(z^2-25)}}}


{{{12z/(z^2-25)}}}