Answer with explanation:
A Rule which expresses that for every input, the output is an even number can be written in many ways
f(x)=2 x , where x is any Integer.
f(n)=4n, where n is any Integer.
f(s)=6s, where s is any Integer.
f(k)=8k, where k is any Integer.
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There can be many more expressions.
In these expressions,if you replace,x ,n,s and ,k by any integer , the result will be an Even Number(Positive Even Number or Negative Even Number).