$\text{Giải thích các bước giải:}$
$a, x² + 5x$
$\text{Cho x² + 5x = 0}$
$⇒ x(x + 5) = 0$
⇒ \(\left[ \begin{array}{l}x=0\\x+5=0\end{array} \right.\)
⇒ \(\left[ \begin{array}{l}x=0\\x=-5\end{array} \right.\)
$b, 3x² + 4x$
$\text{Cho 3x² + 4x = 0}$
$⇒ x(3x + 4) = 0$
⇒ \(\left[ \begin{array}{l}x=0\\3x+4=0\end{array} \right.\)
⇒ \(\left[ \begin{array}{l}x=0\\3x=-4\end{array} \right.\)
⇒ \(\left[ \begin{array}{l}x=0\\x=\dfrac{-4}{3}\end{array} \right.\)
$c, 5x^{5} + 10x$
$\text{Cho 5x^{5} + 10x = 0}$
$⇒ 5x(x^{4} + 2) = 0$
⇒ \(\left[ \begin{array}{l}5x=0\\x^{4}+2=0\end{array} \right.\)
⇒ \(\left[ \begin{array}{l}x=0\\x^{4}=-2\end{array} \right.\)
⇒ \(\left[ \begin{array}{l}x=0\\L\end{array} \right.\)
$⇒ x = 0$
$d, x³ + 27$
$\text{Cho x³ + 27 = 0}$
$⇒ x³ = -27$
$⇒ x³ = (-3)³$
$⇒ x = -3$
$\text{Chúc bạn học tốt !}$
