>>386
f(x) = 2 -3x +4x^3

y = f'(a) (x-a) + f(a) が x = a での y = f(x) の接線の式

f'(x) = -3 + 12x^2
x = 1 をいれて
f'(1) = 9なので

y = 9 (x-1) + f(1) = 9(x-1) + 3 = 9x -6