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如何求带绝对值的单边极限
是这样的:
limx=>-7^- (x+5)*[|x+7|/(x+7)]
limx=>-7^+ (x+5)*[|x+7|/(x+7)]
人气:137 ℃ 时间:2020-01-26 14:47:04
解答
lim(x→-7-0)(x+5)*[|x+7|/(x+7)]
= lim(x→-7-0)(x+5)*[(-1)(x+7)|/(x+7)]
= (-1)lim(x→-7-0)(x+5)
= (-1)(-7+5)
= 2,
lim(x→-7+0)(x+5)*[|x+7|/(x+7)]
= lim(x→-7-0)(x+5)*[(x+7)|/(x+7)]
= lim(x→-7-0)(x+5)
= (-7+5)
= -2.不好意思,能解释下绝对值的问题吗?  函数 |x+7| 看成分段函数  |x+7| = (-1)(x+7),x < -7,     = x+7,x >= -7。求极限时,  若x→-7-0,|x+7| 取 (-1)(x+7) 来计算;  若 x→-7+0,|x+7| 取 x+7 来计算。就这么简单。
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