This is a problem that I had a tough time solving under 3 minutes. Any advice on how to solve it, and maybe a shortcut?
I could solve it in less than 3 min even thru traditional way.
expand as (a+b)^2
(9+sqrt(80))+(9-sqrt(80))+2(sqrt(9+sqrt(80)))(sqrt(9-sqrt(80)))
=> 9+9+2(sqrt(9+sqrt(80))(9-sqrt(80))) the last part is (a+b)(a-b)
=> 18+2(sqrt(9^2-80))
=> 18+2(1)
=>20
