[a,b]x(a,b)=axb
[a,b]x21=15435
[a,b]=15435 :21=735
[a,b]=c.m.m.m.c
a=d*x si b=d*y unde d=21 si x,y numere prime intre ele
a=21x si b=21y
m=a*x si m=b*y unde m=735
735=a*x de unde a=735/x
735=b*y de unde b=735/x
21x+21y=15435 | : 21
x+y=735
735/x+735/y=15435
735*(1/x+1/y)=15345 |:735
1/x+1/y=21
y+x=21xy
735=21xy
xy=735/21
xy=35
x=5
y=7
a=21*5=105
b=21*7=147
verificare : 105*147=15435
