题目内容
先化简,再求值:(
-
)+
,其中x=-1.
x+2 |
x2-2x |
x-1 |
x2-4x+4 |
x-4 |
x |
原式=[
-
]+
=[
-
]+
=
+
=
+
=
=
,
当x=-1时,原式=
=
.
x+2 |
x(x-2) |
x-1 |
(x-2)2 |
x-4 |
x |
=[
x2-4 |
x(x-2)2 |
x2-x |
x(x-2)2 |
x-4 |
x |
=
x2-4-x2+x |
x(x-2)2 |
x-4 |
x |
=
x-4 |
x(x-2)2 |
x-4 |
x |
=
(x-4)(x-2)2 |
x(x-2)2 |
=
x3+20x-16 |
x(x-2)2 |
当x=-1时,原式=
-1-20-16 |
-1×(-1-2)2 |
37 |
9 |
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