1. **State the problem:** Factor the expression $$y=\frac{3}{9}x^2 - 3$$. 2. **Simplify the coefficients:** $$\frac{3}{9} = \frac{1}{3}$$, so the expression becomes $$y=\frac{1}{3}x^2 - 3$$. 3. **Rewrite the expression:** $$y=\frac{1}{3}x^2 - 3 = \frac{1}{3}x^2 - \frac{9}{3}$$. 4. **Factor out the common factor $$\frac{1}{3}$$:** $$y=\frac{1}{3}(x^2 - 9)$$. 5. **Recognize the difference of squares:** $$x^2 - 9 = (x - 3)(x + 3)$$. 6. **Write the fully factored form:** $$y=\frac{1}{3}(x - 3)(x + 3)$$. **Final answer:** $$y=\frac{1}{3}(x - 3)(x + 3)$$.