1968 AMC 12 第 9 题
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所有题目均经美国数学协会（MAA）官方合法授权使用。
9.
满足 的所有实数 之和为：
The sum of the real values of satisfying is:
小提示：
等式两边均非负，可将两边平方
Square both sides; both sides are nonnegative
大提示：
利用所得二次方程的根之和
Use the sum of the roots of the resulting quadratic
解答：
平方后得到 ，即 。两个根都满足原绝对值方程，它们的和为 。
因此，正确答案是 E。
Squaring gives or Both roots satisfy the original absolute-value equation, and their sum is
Therefore, the correct answer is E.
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