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> ①计算:|-3|+3•tan30°-3-8-0②先化简再求值:(x+2)(x-2)+x(3-x),其中x=2+1.-数学
①计算:|-3|+3•tan30°-3-8-0②先化简再求值:(x+2)(x-2)+x(3-x),其中x=2+1.-数学
题目简介
①计算:|-3|+3•tan30°-3-8-0②先化简再求值:(x+2)(x-2)+x(3-x),其中x=2+1.-数学
题目详情
①计算:|-3|+
3
•tan30°-
3
-8
-
0
②先化简再求值:(x+2)(x-2)+x(3-x),其中x=
2
+1.
题型:解答题
难度:中档
来源:不详
答案
①原式=3+
3
×
3
3
-2-1=3+1-2-1=1;
②原式=x2-4+3x-x2
=3x-4.
当x=
2
+1时,
原式=3(
2
+1)-4
=3
2
+3-4
=3
2
-1
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题目简介
①计算:|-3|+3•tan30°-3-8-0②先化简再求值:(x+2)(x-2)+x(3-x),其中x=2+1.-数学
题目详情
②先化简再求值:(x+2)(x-2)+x(3-x),其中x=
答案
②原式=x2-4+3x-x2
=3x-4.
当x=
原式=3(
=3
=3