f’(x)>0,e^x- 1>; 0,e^x>; 1,x & gt0,
f '(x)& lt; 0,e^x- 1<; 0,e^x<; 1,x & lt0,
The increasing interval of f(x) is (0, +∞), and the decreasing interval is (-∞, 0).
3. The derivative function of cubic function is quadratic function, and the sign problem of quadratic function is well solved.
f’(x)>0,3-3x^2>; 0,x^2<; 1,- 1 & lt; x & lt 1;
f '(x)& lt; 0,3-3x^2<; 0,x^2>; 1, x<- 1, or x> 1;
The increasing interval of f(x) is (-1, 1), and the decreasing interval is (-∞,-1), (1, +∞).
4.
f'(x)=3x^2-2x- 1=(3x+ 1)(x- 1),
F'(x)>0, x <-1/3, or x >1,
f '(x)& lt; 0,- 1/3 & lt; x & lt 1.
The decreasing interval of f(x) is (-1/3, 1), and the increasing interval is (-∞,-1/3), (1, +∞).
Dear friends, your suggestion is right! It's good. However, the equal sign cannot be written as a colon.