Use expressions for odd integers to confirm the conjecture that the product for two odd integers is an odd integer.

2n + 1  et 2n + 3 are two odd integers with n integer
(2n+1)(2n+3) = 4n² + 8n + 3 =2(4n² + 4n) + 3 
2(4n² + 4n) is an even integer so 2(4n² + 4n) + 3 is an odd number 
because the sum of an even number and an odd number is an odd number.