1. Derive, the interval where the derivative is greater than 0 is the interval where the increasing function is less than 0 is the subtraction function.

f'(x)=-3x^2-6x+9

On the right side of the symmetry axis is an increasing interval. On the left is the subtraction interval.

2. According to the increase and decrease interval distribution, find the extreme point, and substitute the extreme point and endpoint value in-2,2 into the function, where the minimum value is the minimum value of the function in this interval.