Let f(x)=-4X^2+8X+13 Find g'(3) Show that the linear approxi

Let f(x)=-4X^2+8X+13 Find g'(3) Show that the linear approximation to g(3+△x) always gives an answer which is too large,regardless of whether △x is positive or negative.Interpret your answer geometrically by drawing graph of g and its tangent line when x=3.
这道题的意思,我没有完全理解,