4xy=k . xy
400+xy=k . xy
xy=400/(k-1), k∈N, K>1
xy=2^4 . 5^2/(k-1) ⇒ k-1|400
divizorii naturali ai lui 400 sunt:
D400=1,2,4,5,8,10,16,20,25,40,50,80,100,200,400
dintre acestia cei cu 2 cifre sunt xy
k-1=40, xy=10
k-1=25, xy=16
k-1=20, xy=20
k-1=16, xy=25
k-1=10, xy=40
k-1=8, xy=50
k-1=5, xy=80
