Question

先化简，再求值：(

2

x2-2x

-

1

x2-4x+4

)÷

x-4

x

，其中x=

1

2

．

Answer 1

(

2

x2-2x

-

1

x2-4x+4

)÷

x-4

x

=(

2

x( x-2)

-

1

(x-2)2

)÷

x-4

x

=(

2(x-2)

x(x-2)2

-

x

x(x-2)2

)•

x

x-4

=

x-4

x(x-2)2

•

x

x-4

=

1

(x-2)2

，
当x=

1

2

时，原式=

1

(x-2)2

=

4

9

．