1. The problem appears to involve simplifying and solving algebraic expressions involving powers and variables. 2. Let's start by interpreting the expression: $$7(9x)^2 - 9x^2$$. 3. Recall the rule for powers: $$(ab)^2 = a^2 b^2$$. 4. Applying this, we get: $$7(9^2 x^2) - 9x^2 = 7(81x^2) - 9x^2$$. 5. Simplify the multiplication: $$7 \times 81 x^2 - 9x^2 = 567x^2 - 9x^2$$. 6. Combine like terms: $$567x^2 - 9x^2 = (567 - 9)x^2 = 558x^2$$. 7. The simplified expression is $$558x^2$$. 8. If the problem involves solving an equation such as $$HQ^2 - 662 - 1862 = 0$$, it seems incomplete or mistyped; please clarify if needed. Final answer: $$558x^2$$