Set 16: Quadratic Equations (Intermediate)

Choice A is correct. Choice A is the correct answer. 1. Formula: $\Delta = b^2 - 4 ac$. 2. If $a$ and $c$ have opposite signs, their product $ac$ is negative. 3. Therefore, $-4 ac$ becomes a positive number (subtracting a negative). 4. Since $b^2 \geq 0$, adding a positive number guarantees the result is positive. 5. Thus, there are always two real roots. Choice B is incorrect. Choice C is incorrect. Choice D is incorrect.