a rational number is defined as a number that can be expressed in the form a/b where b≠0
the set of integers includes positive and negative counting numbers and 0
so like -4,-3,-2,-1,0,1,2,3,4.... etc
any integer can be written as the same integer over 1
some examples
-4=-4/1
3=3/1
100=100/1
etc
so yes, any integer can be expressed as a rational number