Răspuns :
se aplica formula (a+b)^3=a^3+3a^2b+3ab^2+b^3
a=3x, b=1
(3x+1)^3=(3x)^3+3(3x)*1^2+3(3x)^2*1+1^3=
27x^3+9x+27x^2+1
a=3x, b=1
(3x+1)^3=(3x)^3+3(3x)*1^2+3(3x)^2*1+1^3=
27x^3+9x+27x^2+1