make sure you plot each number on the right axis. : )
missing constant: 100
perfect square (a - b)^2 = a^2 - 2ab + b^2
in this case
20x = 2 * x * 10
10^2 = 100
(x - 10)^2 = x^2 - 20x + 100
which part of the graph best represents the solution set to th...