Find $x,y$ such that $x=4y$ and $1$-$9$ occur in $x$ or $y$ exactly once. 
$x$ is a $5$-digits number, while $y$ is $4$-digits number. $x=4y$, and they used up all numbers from 1 to 9. Find $x,y$.

Can someone give me some ideas please? Thank you.

Here are the $x,y$ pairs a quick bit of code found.
15768 3942
17568 4392
23184 5796
31824 7956
No insight to offer at the moment I'm afraid..
