Set 9: Exponential Functions

Choice A is correct. Choice A is the correct answer. The y-intercept occurs when $x = 0$. 1. Substitute: $y = 200(0.9)^0 = 200(1) = 200$. 2. Point: The graph crosses the y-axis at $(0, 200)$. Strategic Tip: For $y = ab^x$, the y-intercept is always $(0, a)$ since $b^0 = 1$. Choice B is incorrect because this reverses the coordinates. Choice C is incorrect because 0.9 is the base, not a coordinate. Choice D is incorrect because this is a point on the graph but not the y-intercept.