Question 174086
{{{ (a-1)/(a+1) + (a+1)/(a-1)}}}  you need to get everything over a common denominator first. That would be (a+1)(a-1)
{{{ ((a-1)(a-1))/((a+1)(a-1)) + ((a+1)(a+1))/((a-1)(a+1))}}} 
{{{ ((a-1)^2)/((a+1)(a-1)) + ((a+1)^2)/((a-1)(a+1))}}} 

Now that you have a common denominator, you add fractions just like you did with arithmetic.

{{{ ((a-1)^2 +(a+1)^2)/((a-1)(a+1))}}} 
{{{(a^2 -2a + 1 + a^2 + 2a + 1)/(a^2 - 1)}}}
{{{(2a^2 + 2)/(a^2 -1)}}}