Respuesta :

Answer:

  [tex]x=\pm2\sqrt{10}[/tex]

Step-by-step explanation:

You want to solve ...

  [tex]40 -x^2=0\\\\40=x^2\qquad\text{add $x^2$}\\\\\pm\sqrt{40}=x\qquad\text{take the square root}\\\\\boxed{x=\pm2\sqrt{10}}\qquad\text{simplify}[/tex]