Respuesta :

[tex]\bf 40-x^2=0\implies 40=x^2\implies \pm\sqrt{40}=x \\\\\\ \pm\sqrt{2^2\cdot 10}=x \implies \pm 2\sqrt{10}=x[/tex]
Divide 40 and 20 by 2, the 2 cancels out, bring down the variable, 20= 0