2. Monotone subtraction interval: (negative infinity,-2)&; (0,2)

Monotonically increasing interval: (-2,0)&; (2, positive infinity)

3.？ K & lt- 1,? No answer

K=- 1，？ Two solutions

- 1 & lt； K<3 and 4 solutions

K=3，？ Three solutions

k & gt3? , 2 solutions