∵f′(x)=-3x^2-3,
设切点坐标为(t,-t ^3-3t),
则切线方程为y-(-t ^3-3t)=-3(t ^2+1)(x-t),
∵切线过点P(2,-6),
∴-6-(-t^3-3t)=-3(t^2+1)(2-t),
化简得-2t^3+6t^2=0,∴t=0或t=3.
∴切线的方程:3x+y=0或30x+y-54=0.
∵f′(x)=-3x^2-3,
设切点坐标为(t,-t ^3-3t),
则切线方程为y-(-t ^3-3t)=-3(t ^2+1)(x-t),
∵切线过点P(2,-6),
∴-6-(-t^3-3t)=-3(t^2+1)(2-t),
化简得-2t^3+6t^2=0,∴t=0或t=3.
∴切线的方程:3x+y=0或30x+y-54=0.