4)
( √ 10 + √ 5 ) / √ 5 = ( √ 5 * ( √ 2 + 1 )) / √ 5 = √ 2 + 1
5)
( 23 - √ 23 ) / √ 23 = ( √ 23 * ( √ 23 - 1 )) / √ 23 = √ 23 - 1
6)
( √ 24 - √ 28 ) / ( √ 54 - √ 63 ) = ( 2 √ 6 - 2 √ 7 ) / ( 3 √ 6 - 3 √ 7 ) =
= ( 2 * ( √ 6 - √ 7 )) / ( 3 * ( √ 6 - √ 7 )) = 2/3