Explicație pas cu pas:
15. (a;b)=18 => a=18x si b=18y unde (x;y)=1
a*b=3240 => 18x*18y=3240 => 324*x*y=3240 => x*y=10
Avem cazurile:
x=1 si y=10 => a=18 si b=180
x=10 si y=1 => a=180 si b=18
x=2 si y=5 => a=36 si b=90
x=5 si y=2 => a=90 si b=36
Problema are 4 solutii
16. 2451:n=c1 r=31=> n*c1+31=2451=>n*c1=2420
1227:n=c2 r=17=>n*c2+17=1227=>n*c2=1210
579:n=c3 r=29=>n*c3+29=579=>n*c3=550
=>
n|2420
n|1210
n|550
=> n-divizor comun 2420,1210,550 => n|(2420,1210,550) =>
n|110 => n€{1,2,5,10,11,110}
dar cum n>31 => n=110
