Question

Giúp mình câu 7 ạ 

Answer 1

`x^3 -2x-x+2=0`

`<=> (x^3 -x)-(2x-2)=0`

`<=> x(x^2 -1)-2(x-1)=0`

`<=> x(x-1)(x+1)-2(x-1)=0`

`<=> (x-1)(x^2 +x-2)=0`

`<=> (x-1)(x^2 +2x-x-2)=0`

`<=> (x-1)[x(x+2)-(x+2)]=0`

`<=> (x-1)(x+2)(x-1)=0`

`<=> (x-1)^2 (x+2)=0`

\(< =>\left[{}\begin{matrix}x-1=0\\x+2=0\end{matrix}\right.\\ < =>\left[{}\begin{matrix}x=1\\x=-2\end{matrix}\right.\)