$a$) $(2x+4)^{30} = 0$
$⇔ 2x+4 = 0$
$⇔ 2x = -4$
$⇔ x = -2$
Vậy $x=-2$.
$b$) $x^{10} = x$
$⇔ x^{10} - x =0$
$⇔ x.(x^{9} - 1) = 0$
$⇒$ \(\left[ \begin{array}{l}x=0\\x=1\end{array} \right.\)
Vậy $x$ $∈$ `{0;1}`.
$c$) $x^{20} - x^2 = 0$
$⇔ x^2.(x^{18} - 1) = 0$
$⇒$ \(\left[ \begin{array}{l}x=0\\x=1\\x=-1\end{array} \right.\)
Vậy $x$ $∈$ `{0;±1}`.
$d$) $x^{15} =x$
$⇔ x^{15} - x = 0$
$⇔ x.(x^{14} - 1) = 0$
$⇒$ \(\left[ \begin{array}{l}x=0\\x=1\\x=-1\end{array} \right.\)
Vậy $x$ $∈$ `{0;±1}`.
$e$) $(x-5)^4 = (x-5) ^64$
$⇔ (x-5)^4 - (x-5)^6 = 0$
$⇔ (x-5)^4.[1 - (x-5)^2] = 0$
$⇒$ \(\left[ \begin{array}{l}x-5=0\\x-5=1\\x-5=-1\end{array} \right.\)
$⇔$ \(\left[ \begin{array}{l}x=5\\x=6\\x=4\end{array} \right.\)
Vậy $x$ $∈$ `{4;5;6}`.
