68 + 48sqrt(2) = 4.( 17 + 12sqrt(2)) = 4.[3 + 2.sqrt(2)]^2 = [6 + 4sqrt(2)]^2                   mas 6 + 4sqrt(2) = [2 + sqrt(2)]^2 logo  68 + 48sqrt(2) = [2 + sqrt(2)]^4

25 + 22sqrt(2) = 1^3 + [2sqrt(2)]^3 + 3.[1].[2sqrt(2)].[1 + 2sqrt(2)] = [1 + 2sqrt(2)]^3 logo

o valor da expressao será de 2 + sqrt(2) - [1 + 2sqrt(2)] = 1 - sqrt(2)