Answer
$5, -5$
Work Step by Step
For the equation $3x^2 -75 = 0$, we use the quadratic formula as follows
$$
x=\frac{-b \pm \sqrt{b^{2}-4 a c}}{2 a},
\\
a=3, \quad b=0, \quad c=-75
.$$
That is, $$ x=\frac{0 \pm \sqrt{0+900}}{6 }=\frac{\pm30}{6 }=5, \ or, \ -5
.$$
Check the result:
$$
3(5)^2-75=75-75=0, \quad
3(-5)^2-75=75-75=0
.
$$
