Question 825454
This is a question about Completing The Square.
Simplify what you first can, and then complete the square, simplify more, and put into form of {{{(x-h)^2+k=0}}}.


{{{x^2+7x-x^2=2x^2+6-x^2}}}
{{{7x=(2-1)x^2+6}}}
{{{7x=x^2+6}}}
{{{0=x^2+6-7x}}}
{{{x^2-7x+6=0}}}, general form.


The part, {{{x^2-7x}}}, represents the area of a rectangle, x(x-7).  You could draw this and figure which region beyond the square portion to cut in half and arrange along another edge, and form an expression for the missing square corner...


The square term to add and subtract is {{{(-7/2)^2=49/4}}};
{{{x^2-7x+6+49/4-49/4=0}}}
{{{x^2-7x+49/4+6-49/4=0}}}
{{{(x^2-7x+49/4)+6-49/4=0}}}
{{{(x-7/2)^2+6*4/4-49/4=0}}}
{{{(x-7/2)^2+(24-49)/4=0}}}
{{{highlight((x-7/2)^2-25/4=0)}}}, DONE.