已知函数f(x)=x三次方-3X

3个回答

  • (1)f(x)=x³-3x,求导得f'(x)=3x²-3

    令f'(x)≥0以求f(x)的单调增区间,得3x²-3≥0,解得x≤-1或x≥1

    令f'(x)≤0以求f(x)的单调减区间,得3x²-3≤0,解得-1≤x≤1

    从而可知,当x∈(-3,3/2)时,

    f(x)在x∈(-3,-1]∪[1,3/2)上单调递增,在x∈[-1,1]上单调递减.

    经计算:f(-3)= -18,f(1)= -2,f(1)=2

    f(-3)