Let A be a non-empty set such that A × A has 9 elements among which are found (-1,0) and (0,1), then
We have (-1,0)∈ A×A and (0,1)∈A×A ⇒ -1,0,1 ∈ A
But A×A has 9 elements. Therefore, A has 3 elements. Hence A={-1,0,1}