Question 840850
Do you mean this?
{{{3/(sqrt(2)-5i)}}}


You do NOT "multiply by the opposite of the denominator".  Multiply numerator and denominator by the conjugate of the denominator!


{{{(3/(sqrt(2)-5i))((sqrt(2)+5i)/(sqrt(2)+5i))}}}----notice how this will produce difference of two squares.
{{{3(sqrt(2)+5i)/(2-25i^2)}}}
{{{3(sqrt(2)+5i)/(2+25)}}} --------because {{{i*i=-1}}}
{{{3(sqrt(2)+5i)/27}}}
{{{highlight((1/9)sqrt(2)+(5/27)i)}}}