Question 154365
Just like in arithmetic, you cannot add fraction until they have a common denominator. Same for algebra

{{{(6)/(z-6)+(6)/(z+6)}}}

{{{((6)(z+6))/((z-6)(z+6)) +((6)(z-6))/((z+6)(z-6))}}}
{{{((6z+36) + (6z-36))/((z+6)(z-6))}}}
{{{(12z)/((z+6)(z-6))}}}
{{{(12z)/(z^2-36)}}}