Question

Determinati numerele prime a si b, stiind ca 7a + 10b = 105

Answer 1

7a+10b=105
a,b = nr. prime

10b ==> ultima sa cifra e 0  ==> a=5 <==> 5x7=35, ultima cifra 5+0(de la 10b)=105

35+10b+105l-35
10b=70
==>b=7

sau

l = divide

7a+10b=105
a , b = nr. prime
7a l 105 ==> 10b l 105 ==> b=7
7a+10x7=105
7a+70=105 l -70
7a=35 l :7
a=5