Answer
a) $x= +\sqrt 7,-\sqrt7$
b) $x=-2$
c) $x=3$
d) $x=+2,-2$
Work Step by Step
a) $x^{2}-7=0$
$x^2=7$
$x= +\sqrt 7,-\sqrt7$
b) $x^{3}+8=0$
$x^{3}=-8$
$x=\sqrt[3] -8$
$x=-2$
c) $2x^{3}-54=0$
$2x^{3}=54$
$x^{3}=27$
$x=\sqrt[3] 27$
$x=3$
d) $x^{4}=16$
$x=\sqrt[4] 16$
$x=+2,-2$
