Determinati numerele a,b,c direct proportionale cu7, 14 , 21, daca 3(a+2b+3c)= 7abc

Răspuns :

a=7k, b=14k, c=21k atunci
3(7k+28k+63k)=7x7kx14kx21k
3x98k=7x98k^2x21xk adica k^2=1/49 k=1/7 sau k=-1/7 deci:
a=1 a=-1 b=2 b=-2 c=3 c=-3