Answer:
21. 
 
22. y² = 4a ( x + 2 ) is f' and the other one is f
23. a. At x = -1
23. b. At x = -3, -1, and 2.
Explanation:
21. It is given that, 

⇒ 
 {Differentiating with respect to x}
⇒ 
 {Again differentiating with respect to x} (Answer}
22. One of the graph is a parabola having equation y² = 4a ( x + 2 ) .......... (1) , where a is a constant.
If this is f then f' will be a linear equation i.e. a straight line but the other graph is not linear. 
Therefore, equation (1) is f' and the other one is f. (Answer)
23. a. h(x) is not continuous at x = -1
23. b. h(x) is not differentiable at x = -3, -1 and 2 (Answer)