Răspuns:
Explicație pas cu pas:
(a+b)/4=(b+c)/5=(c+a)/7=2(a+b+c)/(4+5+7)=(a+b+c)/8
(a+b)/4=(a+b+c)/8 2a+2b=a+b+c a+b-c=0
(b+c)/5=(a+b+c)/8 8b+8c=5a+5b+5c 5a-3b-3c=0 sist de grad 1 cu 3 nec
(c+a)/7=(a+b+c)/8 8a+8c=7a+7b+7c a-7b+c=0
a+b-c=0
a-7b+c=0 2a-6b=0 a-3b=0
5a-3b-3c=0
3a-21b+3c=0 8a-24b=0 a-4b=0 Sistemul nu e determinat.