Question
Suppose that the number of elements in set $A$ is $p$, the number of elements in set $B$ is $q$ and the number of elements in $A \times B$ is 7, then $p^2+q^2=$
Suppose that the number of elements in set $A$ is $p$, the number of elements in set $B$ is $q$ and the number of elements in $A \times B$ is 7, then $p^2+q^2=$