Question 856143
Use the FOIL method,
{{{ (x + (3+5i))^2 =(x + (3+5i))(x + (3+5i))}}}
First : {{{x^2=x^2}}}
Outer : {{{x(3+5i)=(3+5i)x}}}
Inner : {{{(3+5i)x=(3+5i)x}}}
Last : {{{(3+5i)(3+5i)=9+15i+15i+25i^2=(9-25)+30i=-16+30i}}}
Add it all together,

{{{ (x + (3+5i))^2 =x^2+2(3+5i)x-16+30i}}}