True. Proof: Suppose m is any even integer and n is any odd
integer. [We must show that m2 + 3n is odd.] By properties 1
and 3 of Example 4.2.3, m2 is even (because m2 = m·m)
and 3n is odd (because both 3 and n are odd). It follows
from property 5 [and the commutative law for addition] that
m2 + 3n is odd [as was to be shown].