2a)
| Let P(n) be the claim: | n | (2i - 1) | = | n2 | for all integers n  1. | 
| S | |||||
| i = 1 | |||||
| P(1) is the statement: | 1 | (2i - 1) | = | 12. | 
| S | ||||
| i = 1 | ||||
| P(k) is the statement: | k | (2i - 1) | = | k2. | 
| S | ||||
| i = 1 | ||||
| P(k+1) is the statement: | k + 1 | (2i - 1) | = | (k + 1)2. | 
| S | ||||
| i = 1 | 
For a proof by induction, you first need to check that the statement P(1) is true. Then assume that P(k) is true and use this to show that P(k + 1) is true.