For f(x)=2x416x2+6 find the following. (A) f(x) (B) The slope of the graph of f at x=3 (C) The equation of the tangent line at x=3 (D) The value(s) of x where the tangent line is horizontal (A) f(x)= (B) At x=3, the slope of the graph of f is (C) At x=3, the equation of the tangent line is y= (D) The tangent line is horizontal at x= (Use a comma to separate answers as needed.)