函数的导数:y' = 3 - 3x²
此为曲线上某点的切线的斜率.
当x = 2时,曲线上在x = 2处的切线的斜率:k = 3 - 3*2² = -9
所以过点A（2,-2）的切线方程:
y - (-2) = -9*(x - 2)
化简:9x + y -16 = 0