x²-4x+1=0 x²+1=4x
（1）x + 1/x
= x²+1/x=4x/x=4
(2)x² + 1/x²
=(x +1/x)²-2
=4×4-2=14
（3）x - 1/x
=±√x² + 1/x²-2
=±√14-2
=±2√3
（4）x^4+ 1/x^4
=(x² + 1/x²)²-2
=14²-2
=194