Question

Giải phương trình :\(\left(x+2\right)^3\)-\(\left(x-2\right)^3\)=12x(x-1)-8

Answer 1

(x+2)³-(x-2)³=12x(x-1)-8

<=> x³+6x²+12x+8-x³+6x²-12x+8=12x²-12x-8

<=>12x²+16=12x²-12x-8

<=>12x=-24

<=>x=-2

Answer 2

\(\left(x+2\right)^3-\left(x-2\right)^3=12x\left(x-1\right)-8\)

\(\left(x^3+6x^2+12x+8\right)-\left(x^3-6x^2+12x-8\right)=12x^2-12x-8\)

\(x^3+6x^2+12x+8-x^3+6x^2-12x+8=12x^2-12x-8\)

\(12x^2+16-12x^2+12x+8=0\)

\(24+12x=0\Leftrightarrow12x=-24\Leftrightarrow x=-2\)