What is the correct formula that would result from the combination
of the two ionic species?

The correct formula : BeSO₄

Chemical formula shows the composition number of the constituent atoms

Polyatomic ion consists of 2 or more ions

The equal charge of the two ions will cancel each other out, while the different charges of the two ions will be crossed each other

Be²⁺ (monatomic ion) has a positive charge of +2, while SO₄²⁻ (polyatomic ion) has a negative -2 charge, so that the two charges with the same magnitude but with different charges cancel each other out so that the compound form is BeSO4