Question 1067148
Strange way to ask for "completing the square".


{{{(x+d)(x+d)=x^2+2dx+d^2=x^2+tx+1/3}}}


{{{system(d^2=1/3, and, 2d=t)}}}



Your value for d is  {{{(1/sqrt(3))(sqrt(3)/sqrt(3))=sqrt(3)/3}}}
or more like
{{{system(d=sqrt(3)/3,or,d=-sqrt(3)/3)}}}



The term, tx, to complete the square to form the square quadratic trinomial,  is  {{{system(t=2(sqrt(3))x/3,OR,-2(sqrt(3))x/3)}}}.