Statement :
is divisible by
.
The statement is False.
\Proof :
\Let
be the statement
is divisible by
.
is the statement that
is divisible by
,
is true since
which is divisible by
.
Assume
is true where
is a positive integer and we have to prove that
must be
true i.e., show that
for some integer
implies that
is divisible by
.
Plug in differerent values :
\For
:
which is not divisible by
but divisible by
.
For
:
which is divisible by
.
For
:
which is not divisible by
but divisible by
.
Therefore,
is divisible by
only when
is an odd number.
The expression
is not divisible by
.