15 For each function, determine the coordinates of the point(s) on the curve at which the gradient has the given value. a f(x) = 5--3x3 gradient =-9 b g(x) = 2x2 - 3x+4 gradient = 5 16 Sketch the graphs of each function and clearly indicate the intercepts and turning points. a y=x3 - 3x2 b y= x(x- 1)(x+1)