First we need to factor trinomial $ \color{blue}{ x^2-3 } $ and than we use factored form to solve an equation $ \color{blue}{ x^2-3 = 0} $.
Since the quadratic trinomial cannot be factored out we solved the problem using quadratic formula.
THE ALTERNATIVE SOLUTION:
Isolate the squared variable term:
$$ x^2 = 3 $$Solve for x:
$$ x_1 = \sqrt { 3 } $$$$ x_2 = -\sqrt { 3 } $$