Question 628730
{{{3/(3-sqrt(13))}}}
Multiply by {{{(3+sqrt(13))/(3+sqrt(13))}}}
{{{3(3+sqrt(13))/((3-sqrt(13))(3+sqrt(13)))=3(3+sqrt(13))/(3^2-(sqrt(13))^2)=3(3+sqrt(13))/(9-13)=-3(3+sqrt(13))/4}}}