Question 197563
{{{9/(z-4)+ 9/(z+4)}}}
Since you are trying to add fractions, you must have the same denominator.
A "common denominator" is (z-4)(z+4)
{{{9/(z-4)+ 9/(z+4)}}}
{{{(9/(z-4))((z+4)/(z+4)) + (9/(z+4))((z-4)/(z-4)) }}}
{{{(9(z+4)/((z-4)(z+4))) + (9(z-4)/((z-4)(z+4)))}}}
{{{((9z+36+9z-36)/((z-4)(z+4))) }}}
{{{((18z)/((z-4)(z+4))) }}}
{{{((18z)/(z^2-16)) }}}