(5+с)^3=(5+с)*(5+с)*(5+с)
(5+с)*(5+с)=25+5с+5с+с^2=с^2+5с+25
с^2+5с+25*(5+с)=5с^2+с^3+25с+5с^2+125+25с=
с^3+10с^2+50с+125
Проверь так?
(5+с)^3=(5+с)*(5+с)*(5+с)
(5+с)*(5+с)=25+5с+5с+с^2=с^2+5с+25
с^2+5с+25*(5+с)=5с^2+с^3+25с+5с^2+125+25с=
с^3+10с^2+50с+125
Проверь так?