If P(n) is the statement “n2 + n” is even”, and if P(r) is true, then P(r + 1) is true
Given. P(n) = n2 + n is even and P(r) is true.
Prove. P(r + 1) is true
Given P(r) is true that means,
= r2 + r is even
Let Assume r2 + r = 2k - - - - - - (i)
Now, (r + 1)2 + (r + 1)
r2 + 1 + 2r + r + 1
= (r2 + r) + 2r + 2
= 2k + 2r + 2
= 2(k + r + 1)
= 2μ
Therefore, (r + 1)2 + (r + 1) is Even.
Hence, P(r + 1) is true