How do you get 20 in (

How do you get the answer 20

$(\pm 2 \sqrt5)^2\\=(\pm 2 \sqrt5)\times(\pm 2 \sqrt5)\\=2*2*\sqrt5*\sqrt5\\=4*5\\=20$

(2√5)²

= 2² x √5²

= 4 x 5

= 20