Question 799571
Think of a quadratic expression as representing a rectangular or square area.  Your equation shows a rectangular area expression, {{{x(x-14)}}}.  The Completing The Square can be shown visually, knowing the side lengths are x and x-14.  A way to rearrange the area giving an empty square piece  makes this empty piece, to be {{{(-14/2)^2=49}}}.


ADD and SUBTRACT 49 to the right hand side.  This will allow....
...Can you proceed with this, or do you need more help?