OG详解-OG6 数学1 Q8

Choice D is correct. It’s given that when x = 0, f(x) = 30. Substituting 0 for x and 30 for f(x) in the given function yields 30 = 0+b, or 30 = b. Therefore, the value of b is 30.
Choice A is incorrect and may result from conceptual or calculation errors. Choice B is incorrect and may result from conceptual or calculation errors. Choice C is incorrect and may result from conceptual or calculation errors.