问题
选择题
已知x+
①x2+
|
答案
∵x+
=2,1 x
∴x2+
=(x+1 x2
)2-2•x•1 x
=22-2=2,∴①正确;1 x
x4+
=(x2+1 x4
)2-2•x2•1 x2
=22-2=2,∴②正确;1 x2
x8+
=(x4+1 x8
)2-2=2,∴③正确1 x4
(x-
)2=(x+1 x
)2-4•x•1 x
=22-4=0,∴④正确;1 x
故选D.