(1)3sin60°+2-1-2cos45°-(2-1)0(2)2x2+6=7x(用配方法解)-数学

题目简介

(1)3sin60°+2-1-2cos45°-(2-1)0(2)2x2+6=7x(用配方法解)-数学

题目详情

(1)
3
sin60°+2-1-
2
cos45°-(
2
-1)0

(2)2x2+6=7x(用配方法解)
题型:解答题难度:中档来源:不详

答案

(1)原式=
3
×
3
2
+class="stub"1
2
-
2
×
2
2
-1
=class="stub"3
2
+class="stub"1
2
-1-1
=0.

(2)移项得:2x2-7x=-6,
x2-class="stub"7
2
x=-3,
配方得:x2-class="stub"7
2
x+(class="stub"7
4
)2=-3+(class="stub"7
4
)2,
(x-class="stub"7
4
)2=class="stub"1
16

开方得:x-class="stub"7
4
class="stub"1
4

解得:x1=2,x2=class="stub"3
2

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