Show that the "rule“
is for a , c ∈ N + {\displaystyle {}a,c\in \mathbb {N} _{+}} (and b , d , b + d ∈ Z ∖ { 0 } {\displaystyle {}b,d,b+d\in \mathbb {Z} \setminus \{0\}} ) never true. Give an example with a , b , c , d , b + d ≠ 0 {\displaystyle {}a,b,c,d,b+d\neq 0} where this rule holds.
(and
)
never true. Give an example with
where this rule holds.
