先化简,再求值:(1?1x+2)÷x2+2x+1x2?4,其中x=2?1
1个回答
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(1?
)÷
=
÷
=
×
=
,
当x=
?1时,
原式=
=
=
1 |
x+2 |
x2+2x+1 |
x2?4 |
=
x+1 |
x+2 |
(x+1)2 |
(x?2)(x+2) |
=
x+1 |
x+2 |
(x+2)(x?2) |
(x+1)2 |
=
x?2 |
x+1 |
当x=
2 |
原式=
| ||
|
| ||
|
2?3
| ||
2 |