Bài 16:
a, $x^2=16$
$⇔x^2=(±4)^2$
$⇔x=±4$
Vậy $x=±4$
b, $x^3=27$
$⇔x^3=3^3$
$⇒x=3$
Vậy $x=3$
c, $2x^3-4=12$
$⇔x^3-2=6$
$⇔x^3=8$
$⇔x^3=2^3⇒x=2$
Vậy $x=2$
d, $5.x^3-5=0$
$⇔x^3-1=0$
$⇔x^3=1=1^3$
$⇒x=1$
Vậy $x=1$
e, $(x+1)^2=16$
$⇔(x+1)^2=(±4)^2$
$⇔$\(\left[ \begin{array}{l}x+1=4\\x+1=-4\end{array} \right.⇔\) \(\left[ \begin{array}{l}x=4-1=3\\x=-4-1=-5\end{array} \right.\)
Vậy $x=3;-5$
f, $(x+1)^3=27$
$⇔(x+1)^3=3^3$
$⇒x+1=3$
$⇔x=3-1=2$
Vậy $x=2$
g, $(x+1)^3=64$
$⇔(x+1)^3=4^3$
$⇒x+1=4$
$⇔x=4-1=3$
Vậy $x=3$
h, $(2.x-1)^3=125$
$⇔(2.x-1)^3=5^3$
$⇒2.x-1=5$
$⇔2.x=6$
$⇔x=6:2=3$
Vậy $x=3$
