Question

Tìm x, biết: a^3-x-x^3+a=0

Answer 1

`-> (a-x)(a^2+ax+x^2) + (a-x) = 0`

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

Mà `a^2 + ax + x^2 + 1 >0 forall x in RR`

`-> a-x=0`

`->x=a`

Answer 2

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