(sqrt7)/(sqrt11+3)=(sqrt7*(sqrt11-3))/((sqrt11+3)(sqrt11-3))
color(red)((a-b)(a+b)=a^2-b^2)
(sqrt7)/(sqrt11+3)=((sqrt7)*(sqrt11-3))/((sqrt11)^2-3^2)
(sqrt7)/(sqrt11+3)=((sqrt7)*(sqrt11-3))/(11-9)
(sqrt7)/(sqrt11+3)=((sqrt7)*(sqrt11-3))/(2)
(sqrt7)/(sqrt11+3)=(sqrt77-3sqrt7)/(2)