(√5+√3)^2=8+2√ 15,

Subtract them to get 3-2 √ 15.

So √ 1 1

(2)(√ 15-√ 13)^2=28-2√ 13√ 15

(√( 13-√ 1 1))^2= 13-√ 1 1

Subtract them to get15+√1-2 √13 √15.

Quadratic15+√1and 2√ 13√ 15.

236+30√ 1 1 & lt； 780

So √ 15-√ 13.

(3)(2/(√6+4))^2=4/(22+8√6)=2/( 1 1+4√6)

(2√2 -√6)^2= 14-8√3

Subtract them to get (242 √ 3+96 √ 2-152-56 √ 6)/(11+4 √ 6).

Easily greater than 0

So 2/(√6+4)>2√2 -√6