Set 14: Exponential Functions

Choice A is correct. Choice A is the correct answer. Identify conditions for asymptote at $y=0$. 1. Standard Form: $y = ab^x$ has asymptote at $y = 0$ (x-axis). 2. Shifted Form: $y = ab^x + k$ has asymptote at $y = k$. 3. Condition: For asymptote at $y=0$, there must be no vertical shift ($k=0$) and $b > 0$. Strategic Tip: Basic exponential $y = ab^x$ always approaches $y=0$ as $x \to \pm \infty$ (depending on $b$). Choice B is incorrect because if $a=0$, the function would be $y=0$ (constant). Choice C is incorrect because $b$ must be positive in exponential functions. Choice D is incorrect because exponential graphs curve, not flat.