OG详解-OG1 数学2 Q9

Choice D is correct. If the graph of  y = g (x) is the result of shifting the graph of y = f (x) down k  units in the xy-plane, the function g  can be defined by an  equation of the form g(x)= f (x)-k. It’s given that f(x)= 7x³  and the graph of y = g (x) is the result of shifting the graph of y = f (x) down 2 units. Substituting 7x³  for f(x) and 2  for k  in the equation g(x)= f (x)-k yields g(x)= 7x³ -2.
Choice A is incorrect and may result from conceptual errors. Choice B is incorrect and may result from conceptual errors. Choice C is incorrect. This equation defines afunction g  for which the graph of y = g (x) is the result of shifting the graph of y = f (x) up, not down,  2 units.