Hello there!
x^2 - (1/x^2)
x = 3 - 2√2 -- (1)
1/x = 1/( 3-2√2 )
= ( 3 + 2√2 ) / (3 - 2√2 )(3+2√2 )
= ( 3 + 2√2 ) / 3² - ( 2√2 )²
3^2 = 9 and 2√2 ² = 8
= ( 3 + 2√2 ) / ( 9 - 8 )
= ( 3 + 2√2) -- (2)
x - 1/x = 3 - 2√2 - ( 3 + 2√2 )
= 6
= 3 - 2√2 - 3 - 2√2
= - 4√2
x² - 1/x² = ( x + 1/x ) ( x - 1/x )
= 6 × ( - 4√2 )
6 x ( -4√2 ) = -24√2