题目
Solve the inequality .
题目中文翻译
解不等式 。
原卷通用作答要求
Answer all questions. You should use a calculator where appropriate.
You must show all necessary working clearly; no marks will be given for unsupported answers from a calculator.
Give non-exact numerical answers correct to 3 significant figures, or 1 decimal place for angles in degrees, unless a different level of accuracy is specified in the question.
请回答所有题目。适当时应使用计算器。必须清楚展示所有必要的计算过程;仅给出计算器答案而没有过程,不予评分。除非题目另有精度要求,非精确数值答案保留 3 位有效数字,以度为单位的角度保留 1 位小数。
解答
解法一
思路
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两边都是非负量,可以等价地平方。把平方差分解,再根据两个一次因子的符号判断。
答题过程
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Squaring is equivalent because both sides are nonnegative. Thus
is equivalent to
or . The two factors have the same sign outside their roots, giving or .
解法二
思路
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也可以先根据 的符号去掉左边绝对值。对正数 , 等价于 。
答题过程
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For , the inequality becomes . This requires both
giving and , hence .
At , the left side is zero and the inequality fails. For , it becomes , requiring and . Thus . Combining gives or .