Question

计算：-2²+（

1

2 -1

）⁰+2sin30°+

x2-1

x2-2x+1

+

x2-2x

x-2

÷x，其中x=

1

2

．

Answer 1

原式=-4+1+2•

1

2

+

(x+1)(x-1)

(x-1) 2

+

x(x-2)

x-2

•

1

x

=-2+

x+1

x-1

+1
=

x+1

x-1

-1
=

2

x-1

，
当x=

1

2

时，原式=

2

1 2 -1

=-4．