Răspuns:
n:4= c1, r=1
n:5= c2, r=1
n:6= c3, r=1
=>
n= 4×c1+1
n=5×c2+1
n=6×c3+1 |-1
=> n-1= 4×c1
n-1= 5×c2
n-1= 6×c3
De aici rezulta ca
=> n-1∈ M[4, 5, 6]
[4, 5, 6]= cel mai mare multiplu comun
[4, 5, 6]= 4×5×6= 120
n-1∈M120= {0, 120, 240,...} |+1 => n= 121