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> (1)求值:2sin30°+4cos60°+tan45°(2)计算:8+18-322(3)解方程:2x2-x-2=0.-数学
(1)求值:2sin30°+4cos60°+tan45°(2)计算:8+18-322(3)解方程:2x2-x-2=0.-数学
题目简介
(1)求值:2sin30°+4cos60°+tan45°(2)计算:8+18-322(3)解方程:2x2-x-2=0.-数学
题目详情
(1)求值:2sin30°+4cos60°+tan45°
(2)计算:
8
+
18
-
3
2
2
(3)解方程:2x
2
-x-2=0.
题型:解答题
难度:中档
来源:不详
答案
(1)原式=2×
class="stub"1
2
+4×
class="stub"1
2
+1=2
class="stub"1
2
;
(2)原式=2
2
+3
2
-
class="stub"3
2
2
=
class="stub"7
2
2
;
(3)∵2x2-x-2=0,
∴x2-
class="stub"1
2
x-1=0,
∴(x-
class="stub"1
4
)2=
class="stub"17
16
,
∴x-
class="stub"1
4
=±
17
4
,
∴x1=
1+
17
4
,x2=
1-
17
4
.
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题目简介
(1)求值:2sin30°+4cos60°+tan45°(2)计算:8+18-322(3)解方程:2x2-x-2=0.-数学
题目详情
(2)计算:
(3)解方程:2x2-x-2=0.
答案
(2)原式=2
(3)∵2x2-x-2=0,
∴x2-
∴(x-
∴x-
∴x1=