(x+ 1/x)^2=9
(昌蔽x+ 1/x)伏扰^2
=x^2 + 1/x^2+2
=9
x^2 + 1/耐厅州x^2
=9-2
=7
7
x^2 + 1/x^2=(x+ 1/x)^2-2=7
因为银陆 X+1/昌戚X=3
所锋迅顷以(X+1/X)^2= X^2+1/X^2+2=9
所有 X^2+1/X^2=7
(x+ 1/x)^2=x^2+2x1/x+1/x^2=9 x^2 + 1/x^2=9-2=7
(x+ 1/x )^2=x^2 + 1/x^2 +2=9,故x^2 + 1/x^2 =7