I am having a hard time creating this FUNCTION to be called later. Please help

Consider the cubic equation: f(x) = Dx3 + Cx2 + Bx + A. The turning points of the curve will occur where the derivative of f is zero. The locations of these zeros can be found by finding the roots (zeros) of the quadratic equation g(x) = 3Dx2 + 2Cx + B. Remember that the roots of a general quadratic equation Q(x) = ax2 + bx+c are: X = B+vb2-4ac 2a , X, = B-vb2-4ac 2a a. [6 points] Using the expressions above, write a MATLAB function that will take as input the coefficients A, B, C, and D, and provide as output the locations of the turning points of function f(x). Remember that there may be zero, one, or two turning points, so your function will need to work intelligently for each case