Answer
$x^2-45=0$
Work Step by Step
As we are given that solution set : {$-3\sqrt 5,3\sqrt 5$}
This implies that $x=-3\sqrt 5,3\sqrt 5$
As per zero-product reverse property, we have $(x+3\sqrt 5)(x-3\sqrt 5)=0$
Now, apply FOIL METHOD
$(x+3\sqrt 5)(x-3\sqrt 5)=0\implies x^2-(3\sqrt 5)^2=0$
or, $x^2-45=0$
