if x `prop z ` and y `prop z`, then xy `prop ` z .

Explanation

x `prop z rArr x =k_(1)z ` (where `k_(1)` = non -zero variation constant ) ………..(1)
y `prop z rArr y =k_(2) z `(where `k_(2)` = non -zero variation constant )……….(2)
`therefore xy =(k_(1)z) (k_(2)z)=k_(1)k_(2)z^(2)=k.z^(2)(where k =k_(1) k_(2) =constant)`
`therefore xy kz^(2)` (where k `ne` 0=variation constant )
`therefore xy prop z^(2)`
`therefore ` The statement is false.