Please help me with this.

It is not possible that (a,b) = 20
The given parameters are:
a, b ∈ P
s, t ∈ Z
In mathematical symbols;
This means that a and b are irrational numbers.
The expression (x,y) belongs to the set of natural numbers i.e.
(x, y) ∈ N
This means that:
(a, b) must be a natural number.
Since a and b are irrational numbers, then
(a, b) ∉ N
Hence, it is not possible that (a,b) = 20
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