Exer. 2.1
Exer. 2.1 a solution which challenges the one above.
Exer. 2.2
Exer. 2.2 another solution
Exer. 2.3
Exer. 2.3 another solution
Exer. 2.4
Exer. 2.4 another solution
Exer. 2.5
Exer. 2.6
Exer. 2.6 another solution
Exer. 2.6 yet another solution
Exer. 2.7
Exer. 2.7 another solution
Exer. 2.8
Exer. 2.8 another solution