Răspunsuri

2014-10-22T14:25:16+03:00
(a,b)=21 => a=21x
                    b=21y, (x,y)=1
a+b=231
21x+21y=231
21(x+y)=231
x+y=231/21=11 => (x,y)∈{(1,10),(2,9),(3,8),(4,7),(5,6),(6,5),(7,4),(8,3),(9,2),(10,1)}
Deci (a,b)∈{(21,210),(42,189),(63,168),(84,147),(105,126),(126,105),(147,84),(168,63),(189,42),(210,21)}