In lieu of any other PhysicsForums sandbox (known to me):
literal copy+paste from https://www.physicsforums.com/help/latexhelp/
$$x = \frac {-b \pm \sqrt{b^2 -4ac}} {2a},$$
literal copy+paste from https://www.physicsforums.com/help/latexhelp/
$$x = \frac {-b \pm \sqrt{b^2 -4ac}} {2a},$$