(1) square, directed:
x? +2+ 1/x? =9
x? + 1/x? =7
②
x? + 1/x?
=(x+ 1/x)(x? -x* 1/x+ 1/x? )
=3*(7- 1)
=3*6
= 18
③
(x- 1/x)?
=(x+ 1/x)? -4*x* 1/x
=9-4
=5
x- 1/x= √5
④
√3+ 1/√3
=√3+√3/(√3*√3)
=√3+√3/3
=4/3*√3