I have a problem with this exercise:
"The curve with equation: y = ax^3 + bx^2 + cx + d has a local maximum point where x=-3 and a local minimum point where x=-1. If the curve passes through the points (0;4) and (1;20), find the equation for y in terms of x"
I get that "d = 4"; "a + b + c=16"; "27a - 6b + c" and "3a - 2b + c" both are equal to 0; and that "2b - 18a is less than zero" while "2b - 6a is greater than zero"
But I'm stuck, and can't seem to find the values for a;b and c.