is a universe
model whose universe is .
+ and x are relations over modulo m.
We need to show that is decidable.
We can clear observe that Ƶm is finite as up to m terms.
So we can easily enumerate all possible values into formula and check if the formula is right or not.
- If it is TRUE, then it belong to .
- If it is NOT TRUE, then it belong to .
Let, Ǝxi such that Put
So, if formula is true for any value of xi then the original value is true.
Now, a model of theory is considered to be decidable if the formula which is true and also belong to the model.
So, by above recursive strategy, we say is decidable.