4k + 7 = - 3 + 5k
7 + 3 = 5k - 4k
k = 10
- - - - - - - - - - - -
Проверка:
4 · 10 + 7 = - 3 + 5 · 10
40 + 7 = 50 - 3
47 = 47
A^3/(a^2 +ab +b^2) +
b^3/(b^2 +bc +c^2) +
c^3/(c^2 +ac +a^2) =20,14 <=>
a^3 -b^3 +b^3/(a^2 +ab +b^2) +
b^3 -c^3 +c^3/(b^2 +bc +c^2) +
c^3 -a^3 +a^3/(c^2 +ac +a^2) =20,14 <=>
(a-b)(a^2 +ab +b^2)/(a^2 +ab +b^2) + b^3/(a^2 +ab +b^2) +
(b-c)(b^2 +bc +c^2)/(b^2 +bc +c^2) + c^3/(b^2 +bc +c^2) +
(a-c)(a^2 +ac +c^2)/(c^2 +ac +a^2) + a^3/(c^2 +ac +a^2) =20,14 <=>
a -b +b^3/(a^2 +ab +b^2) +
b -c +c^3/(b^2 +bc +c^2) +
c -a +a^3/(c^2 +ac +a^2) =20,14 <=>
a^3/(c^2 +ac +a^2) +
b^3/(a^2 +ab +b^2) +
c^3/(b^2 +bc +c^2) =20,14
(2+5+5+5+5+5)/6=27/6=4,5≈5
Ответ: 5 пятерок