4. 240 Find three natural numbers that satisfy the equation , and determine whether the solution set of this equation in the set of natural numbers is finite or infinite.
Solution
[Solution] Since , we have
That is, is a set of solutions to the given equation.
On the other hand, if is a set of solutions to the given equation in the set of natural numbers, then is also a solution, where is any natural number.
Therefore, the set of solutions to the given equation in the set of natural numbers is infinite.
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