Stage 1: Identify that the equation is a quadratic and that the question is asking you to find out which values 'x' fit this equation. Quadratics can be written algebraically in the form ax^{2}+bx+c and have 0, 1 or 2 roots.Stage 2: Notice that the 'b' value is 0 and the 'c' value is a square number. This suggests that the equation can be solved by using the 'Difference of Two Squares'Stage 3: Identify that the root of 9 is 3, and so using the difference of two squares, the equation can be factorised to (x-3)(x+3)=0Stage 4: Solve the newly factorised equation for the two roots of x=3 and x=-3