Whenever you see <em>x </em> next to a 3, and it says that it equals 9, you know that 3•3=9.
The roots, zeros, or solutions (they all means same thing) of an equation are when you graph that equation, x-intercepts are the real roots, zeros, or solutions.
Or set the y equal to zero which does the same job.
Let P be the last point in the triangle you have drawn from AB.. It is isosceles and rectangle hence AB^2=2BP^2 hence AP=BP=sqrt(2).
Let Q be the last point in the triangle you have drawn from CD. By the same reasoning, CQ=DQ=sqrt(2)
What is more, AD=AP+PQ+QD=2sqrt(2)+1
