Answer
$x^2-20=0$
Work Step by Step
As we are given that solution set : {$-2\sqrt 5,2\sqrt 5$}
This implies that $x=-2\sqrt 5,2\sqrt 5$
As per zero-product reverse property, we have $(x+2\sqrt 5)(x-2\sqrt 5)=0$
Now, apply FOIL METHOD
$(x+2\sqrt 5)(x-2\sqrt 5)=0\implies x^2-(2\sqrt 5)^2=0$
or, $x^2-20=0$
