Question: User: -3x squared - 3x squared
1. **State the problem:** Simplify the expression $$-3x^2 - 3x^2$$.
2. **Formula and rules:** When combining like terms, add or subtract the coefficients of the terms with the same variable and exponent.
3. **Combine like terms:** $$-3x^2 - 3x^2 = (-3 - 3)x^2$$.
4. **Simplify the coefficients:** $$-3 - 3 = -6$$, so the expression becomes $$-6x^2$$.
5. **Final answer:** The simplified expression is $$-6x^2$$.