f(x) = 3*x^4-4*x^3-12*x^2+8

[Maple Plot]

matrix([[`x points above:`, -1.000, -.5486, 0., .7756, 1.215, 2.000, 2.685], [`a zero of f ?`, __, __, __, __, __, __, __], [`x-inter of f ?`, __, __, __, __, __, __, __], [`a zero of f ' ?`, __, __, _...