Chapter 9 - Section 9.1 - Solving Quadratic Equations by the Square Root Property - Exercise Set - Page 631: 10

$x=\pm5$

Using the properties of equality, the given equation, $ 3x^2=75 ,$ is equivalent to \begin{array}{l}\require{cancel} x^2=\dfrac{75}{3} \\\\ x^2=25 .\end{array} Taking the square root of both sides, then the solutions of the given equation are \begin{array}{l}\require{cancel} x=\pm\sqrt{25} \\\\ x=\pm\sqrt{(5)^2} \\\\ x=\pm5 .\end{array}