Set 9: Quadratic Equations (Advanced)

Choice A is correct. Choice A is the correct answer. 1. Setup: Base = $b$, Height = $b - 4$. Area = $0.5\times b \times h$. 2. Equation: $0.5b(b - 4) = 30$. 3. Solve: $b(b - 4) = 60 \Rightarrow b^2 - 4 b - 60 = 0$. 4. Factor: $(b - 10)(b + 6) = 0$. 5. Result: $b = 10$ (since base must be positive). Choice B is incorrect because area would be 0.$5 *6*2 = 6$. Choice C is incorrect. Choice D is incorrect.