Set 1: Exponential Functions (Advanced)

Choice A is correct. Choice A is the correct answer. Use the y-intercept to find $k$. 1. Y-intercept: When $x = 0$, $y = k(0.7)^0 = k$. 2. Given: Y-intercept is 140. 3. Conclusion: $k = 140$. Strategic Tip: For $y = ab^x$, the y-intercept always equals $a$. Choice B is incorrect because this is the base, not the coefficient. Choice C is incorrect because this is $140\times 0.7$, the value at $x=1$. Choice D is incorrect because this doesn't match the y-intercept.