若x+1/x=3,则x2+1/x2的值.

问题描述:

若x+

1
x
=3,则x2+
1
x2
的值.

x+

1
x
=3
       (x+
1
x
)
2
=32
x2+2×
1
x
+
1
x2
=9
        x2+
1
x2
=9-2
        x2+
1
x2
=7.