Giải dùm mình với ạ (x+1)³ - (x-1)³ = 6(x²+x+1)

(x+1)³ - (x-1)³ = 6(x²+x+1)

⇔x³+3x²+3x+1-x³+3x²-3x+1-6(x²+x+1)=0

⇔6x²+2-6(x²+x+1)=0

⇔2(3x²+1)-2(3x²+3x+3)=0

⇔2(3x²+1-3x²-3x-3)=0

⇔2(-3x-2)=0

⇔-3x-2=0

⇔-3x=2

⇔x=-2/3

Vậy S={-2/3}