17n+23/15n+28 €N
15n+28|17n+23|×15
15n+28|15n+28|×17
=>
15n+28|255n+345
15n+28|255n+476
---------------------------
15n+28|(255n+476)-(255n+345)
15n+28|131
15n+28€D lui 131 {1, 131}
15n+28=1
15n=1-28 nu apartine lui N
15n+28=131
15n=131-28
15n=103
n=103/15
Sper sa fie bine