Giải thích các bước giải:
Ta có:
$a_n\alpha^n+a_{n-1}\alpha^{n-1}+...+a_1\alpha+a_0=0$
$\Leftrightarrow a_{n-1}\alpha^{n-1}+...+a_1\alpha+a_0=-a_n\alpha^n$
$\Leftrightarrow (a_{n-1}\alpha^{n-1}+...+a_1\alpha+a_0):a_n=-a_n\alpha^n:a_n$
$\Leftrightarrow \dfrac{a_{n-1}}{a_n}\alpha^{n-1}+...+\dfrac{a_1}{a_n}\alpha+\dfrac{a_0}{a_n}=-\alpha^n$
$\Leftrightarrow |\dfrac{a_{n-1}}{a_n}\alpha^{n-1}+...+\dfrac{a_1}{a_n}\alpha+\dfrac{a_0}{a_n}|=|-\alpha^n|$
