what are the coordinates of the various points on this cubic graph?
what would the y-value be
when x = -12?
when x = 16?
maybe use a spreadsheet to ascertain the function
David Wells points out that:
IC is a tangent to the curve at point C and BG is a tangent at G
all cubic curves have rotational symmetry about their point of inflection (E)
and the sum of the x-distances from the point of inflection (E) of the any straight line cutting the curve at three points is always zero (for any cubic)
in the case of a tangent, two of the points are coincident