a) [tex](ab)^2[/tex]. The square power of an odd integer is always an odd integer. For example: [tex]21^2 = 441[/tex]
b) [tex]a^2 - b^2[/tex]. [tex]a^2[/tex] is an even integer and [tex]b^2[/tex] is an odd integer. The difference between both numbers is and odd integer.
c) The product of an even integer (2a) and an odd integer is always a even integer.
d) The product of an even integer (a) and other even integer (2b) is always a even integer.
The answer is c) and d) cases.
