Question

Numerele reale a si b sunt direct proportionale cu 3 si 7 . Stiind ca 2a+4=b, aflati a si b

Answer 1

{a;b} dp {3;7}
2a+4=b
a/3=b/7=k ==> a=3k
                       b=7k
2.3k+4=7k
6k+4=7k
6k-7k=-4
-k=-4 ==> k=4 ==> a=3.4=12
                             b=7.4=28

Answer 2

a=3k b=7k 6k+4=7k  6k-7k=-4 => -k=-4(*-1) =>k=4 
a=3*4 a=12
b=7*4 b=28