(1)计算18+1550-612-2sin45°+13tan260°(2)先化简,再求值:(1x-y-1x+y)÷2yx2-2xy+y2,其中x=1+2,y=1-2.-数学

题目简介

(1)计算18+1550-612-2sin45°+13tan260°(2)先化简,再求值:(1x-y-1x+y)÷2yx2-2xy+y2,其中x=1+2,y=1-2.-数学

题目详情

(1)计算
18
+
1
5
50
-6
1
2
-2sin45°+
1
3
tan260°
(2)先化简,再求值:(
1
x-y
-
1
x+y
2y
x2-2xy+y2
,其中x=1+
2
,y=1-
2
题型:解答题难度:中档来源:不详

答案

(1)原式=3
2
+
2
-3
2
-2×
2
2
+class="stub"1
3
×(
3
)2
=
2
-
2
+1
=1;

(2)原式=class="stub"x+y-x+y
(x+y)(x-y)
÷class="stub"2y
(x-y)2

=class="stub"2y
(x+y)(x-y)
×
(x-y)2
2y

=class="stub"x-y
x+y

x=1+
2
,y=1-
2
时,原式=
1+
2
-1+
2
1+
2
+1-
2
=
2
2
2
=
2

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