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> (1)已知x=2,y=5.求代数式:1-x-yx-2y÷x2-y2x2-4xy+4y2的值.(2)化简求值:(x+2x-2+4x2-4x+4)÷xx-2,其中x=-12.-数学
(1)已知x=2,y=5.求代数式:1-x-yx-2y÷x2-y2x2-4xy+4y2的值.(2)化简求值:(x+2x-2+4x2-4x+4)÷xx-2,其中x=-12.-数学
题目简介
(1)已知x=2,y=5.求代数式:1-x-yx-2y÷x2-y2x2-4xy+4y2的值.(2)化简求值:(x+2x-2+4x2-4x+4)÷xx-2,其中x=-12.-数学
题目详情
(1)已知x=2,y=5.求代数式:
1-
x-y
x-2y
÷
x
2
-
y
2
x
2
-4xy+4
y
2
的值.
(2)化简求值:
(
x+2
x-2
+
4
x
2
-4x+4
)÷
x
x-2
,其中
x=-
1
2
.
题型:解答题
难度:中档
来源:不详
答案
(1)原式=1-
class="stub"x-y
x-2y
•
(x-2y
)
2
(x-y)(x+y)
=1-
class="stub"x-2y
x+y
=
class="stub"x+y-x+2y
x+y
=
class="stub"3y
x+y
,
当x=2,y=5时,原式=
class="stub"3×5
2+5
=
class="stub"15
7
;
(2)原式=
(x+2)(x-2)+4
(x-2
)
2
•
class="stub"x-2
x
=
x
2
(x-2
)
2
•
class="stub"x-2
x
=
class="stub"x
x-2
,
当x=-
class="stub"1
2
时,原式=
-
class="stub"1
2
-
class="stub"1
2
-2
=
class="stub"1
5
.
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题目简介
(1)已知x=2,y=5.求代数式:1-x-yx-2y÷x2-y2x2-4xy+4y2的值.(2)化简求值:(x+2x-2+4x2-4x+4)÷xx-2,其中x=-12.-数学
题目详情
(2)化简求值:(
答案
=1-
=
=
当x=2,y=5时,原式=
(2)原式=
=
=
当x=-