[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:00.59,0:00:03.88,Default,,0000,0000,0000,,让我们来学习解绝对值方程式
Dialogue: 0,0:00:03.88,0:00:05.12,Default,,0000,0000,0000,,先来复习下
Dialogue: 0,0:00:05.12,0:00:07.65,Default,,0000,0000,0000,,当计算一个数值的绝对值时
Dialogue: 0,0:00:07.65,0:00:10.68,Default,,0000,0000,0000,,以-1为例 来计算绝对值
Dialogue: 0,0:00:10.68,0:00:12.26,Default,,0000,0000,0000,,你需要做的是
Dialogue: 0,0:00:12.26,0:00:16.09,Default,,0000,0000,0000,,计算出1与0之间的距离
Dialogue: 0,0:00:16.09,0:00:20.62,Default,,0000,0000,0000,,对-1来说 下面以数轴示例
Dialogue: 0,0:00:20.62,0:00:23.31,Default,,0000,0000,0000,,这个没画好
Dialogue: 0,0:00:23.31,0:00:26.23,Default,,0000,0000,0000,,这是数轴 这是0
Dialogue: 0,0:00:26.23,0:00:28.47,Default,,0000,0000,0000,,这是-1
Dialogue: 0,0:00:28.47,0:00:30.23,Default,,0000,0000,0000,,-1与0之间的距离是1
Dialogue: 0,0:00:30.23,0:00:33.25,Default,,0000,0000,0000,,那-1的绝对值就是1
Dialogue: 0,0:00:33.25,0:00:38.85,Default,,0000,0000,0000,,1和0之间的距离也是1
Dialogue: 0,0:00:38.85,0:00:40.61,Default,,0000,0000,0000,,所以1的绝对值同样是1
Dialogue: 0,0:00:40.61,0:00:43.50,Default,,0000,0000,0000,,也就是说 绝对值为与0之间的距离
Dialogue: 0,0:00:43.50,0:00:45.59,Default,,0000,0000,0000,,来换一种更简单的方式来理解
Dialogue: 0,0:00:45.59,0:00:48.60,Default,,0000,0000,0000,,绝对值其实就是取数值的正值
Dialogue: 0,0:00:48.60,0:00:59.36,Default,,0000,0000,0000,,-7346的绝对值是7346.
Dialogue: 0,0:00:59.36,0:01:00.78,Default,,0000,0000,0000,,理解这点以后 下面
Dialogue: 0,0:01:00.78,0:01:05.05,Default,,0000,0000,0000,,开始学习解绝对值方程式
Dialogue: 0,0:01:05.05,0:01:06.68,Default,,0000,0000,0000,,来看这个方程式
Dialogue: 0,0:01:06.68,0:01:14.50,Default,,0000,0000,0000,,x-5的绝对值等于10
Dialogue: 0,0:01:14.50,0:01:15.90,Default,,0000,0000,0000,,可以这样解读这个等式
Dialogue: 0,0:01:15.90,0:01:18.16,Default,,0000,0000,0000,,也希望能够这样理解 这就是说
Dialogue: 0,0:01:18.16,0:01:23.12,Default,,0000,0000,0000,,x与5之间的距离为10
Dialogue: 0,0:01:23.12,0:01:26.75,Default,,0000,0000,0000,,与5之间的距离是10的数值有几个
Dialogue: 0,0:01:26.75,0:01:29.43,Default,,0000,0000,0000,,大家应该已经想到解法了
Dialogue: 0,0:01:29.43,0:01:31.96,Default,,0000,0000,0000,,不过下面要学习更系统的解法
Dialogue: 0,0:01:31.96,0:01:36.51,Default,,0000,0000,0000,,这个方程式有两种情况
Dialogue: 0,0:01:36.51,0:01:41.80,Default,,0000,0000,0000,,一种是x-5等于10
Dialogue: 0,0:01:41.80,0:01:44.63,Default,,0000,0000,0000,,如果假定绝对值里面的值为10
Dialogue: 0,0:01:44.63,0:01:46.61,Default,,0000,0000,0000,,取绝对值后
Dialogue: 0,0:01:46.61,0:01:48.38,Default,,0000,0000,0000,,会得到10
Dialogue: 0,0:01:48.38,0:01:53.13,Default,,0000,0000,0000,,或者假设x-5等于-10
Dialogue: 0,0:01:53.13,0:01:58.70,Default,,0000,0000,0000,,如果x-5等于-10 取绝对值后
Dialogue: 0,0:01:58.70,0:01:59.95,Default,,0000,0000,0000,,也是10
Dialogue: 0,0:01:59.95,0:02:04.28,Default,,0000,0000,0000,,所以第二种情况是 x-5等于-10
Dialogue: 0,0:02:04.28,0:02:07.73,Default,,0000,0000,0000,,两种情况同时满足这个方程式
Dialogue: 0,0:02:07.73,0:02:08.96,Default,,0000,0000,0000,,先解这个
Dialogue: 0,0:02:08.96,0:02:11.50,Default,,0000,0000,0000,,等式两边加5
Dialogue: 0,0:02:11.50,0:02:14.16,Default,,0000,0000,0000,,得到x=15
Dialogue: 0,0:02:14.16,0:02:17.83,Default,,0000,0000,0000,,再解这个 等式两边加5
Dialogue: 0,0:02:17.83,0:02:20.90,Default,,0000,0000,0000,,x等于-5
Dialogue: 0,0:02:20.90,0:02:21.96,Default,,0000,0000,0000,,得出计算结果
Dialogue: 0,0:02:21.96,0:02:24.91,Default,,0000,0000,0000,,有两个x值满足这个方程式
Dialogue: 0,0:02:24.91,0:02:26.89,Default,,0000,0000,0000,,x可以是15
Dialogue: 0,0:02:26.89,0:02:29.50,Default,,0000,0000,0000,,15-5等于10 取绝对值后
Dialogue: 0,0:02:29.50,0:02:32.69,Default,,0000,0000,0000,,得到10 或者x为-5
Dialogue: 0,0:02:32.69,0:02:36.06,Default,,0000,0000,0000,,-5减5等于-10
Dialogue: 0,0:02:36.06,0:02:39.02,Default,,0000,0000,0000,,取绝对值后 还是10
Dialogue: 0,0:02:39.02,0:02:41.63,Default,,0000,0000,0000,,注意 这两个值
Dialogue: 0,0:02:41.63,0:02:45.75,Default,,0000,0000,0000,,与5之间的距离都是10
Dialogue: 0,0:02:45.75,0:02:48.05,Default,,0000,0000,0000,,再解一个
Dialogue: 0,0:02:48.05,0:02:51.13,Default,,0000,0000,0000,,再来一个
Dialogue: 0,0:02:51.13,0:02:52.18,Default,,0000,0000,0000,,现在有
Dialogue: 0,0:02:52.18,0:02:58.58,Default,,0000,0000,0000,,x+2的绝对值等于6
Dialogue: 0,0:02:58.58,0:02:59.61,Default,,0000,0000,0000,,这说明什么呢
Dialogue: 0,0:02:59.61,0:03:03.13,Default,,0000,0000,0000,,也就是说 要么x+2
Dialogue: 0,0:03:03.13,0:03:07.03,Default,,0000,0000,0000,,也就是绝对值符号里的这个值 它等于6
Dialogue: 0,0:03:07.03,0:03:10.38,Default,,0000,0000,0000,,或者绝对值符号里的这个值
Dialogue: 0,0:03:10.38,0:03:12.05,Default,,0000,0000,0000,,x+2 它等于-6
Dialogue: 0,0:03:12.05,0:03:13.91,Default,,0000,0000,0000,,假设等于-6时
Dialogue: 0,0:03:13.91,0:03:16.21,Default,,0000,0000,0000,,取绝对值后 得到6
Dialogue: 0,0:03:16.21,0:03:20.34,Default,,0000,0000,0000,,那么 假设x+2等于-6
Dialogue: 0,0:03:20.34,0:03:22.88,Default,,0000,0000,0000,,然后 等式两边减2
Dialogue: 0,0:03:22.88,0:03:25.85,Default,,0000,0000,0000,,得到 x等于4
Dialogue: 0,0:03:25.85,0:03:29.78,Default,,0000,0000,0000,,再看这个方程式 两边减2
Dialogue: 0,0:03:29.78,0:03:33.69,Default,,0000,0000,0000,,得到x等于-8
Dialogue: 0,0:03:33.69,0:03:37.24,Default,,0000,0000,0000,,这就是方程式的两种解法
Dialogue: 0,0:03:37.24,0:03:39.74,Default,,0000,0000,0000,,为了加深理解
Dialogue: 0,0:03:39.74,0:03:42.50,Default,,0000,0000,0000,,对于绝对值 可以把它看成是距离
Dialogue: 0,0:03:42.50,0:03:43.94,Default,,0000,0000,0000,,这样重写这个绝对值方程式
Dialogue: 0,0:03:43.94,0:03:50.41,Default,,0000,0000,0000,,x减-2的绝对值等于6
Dialogue: 0,0:03:50.41,0:03:52.76,Default,,0000,0000,0000,,其实就是说
Dialogue: 0,0:03:52.76,0:03:57.59,Default,,0000,0000,0000,,哪些值与-2之间的距离刚好是6呢
Dialogue: 0,0:03:57.59,0:03:59.17,Default,,0000,0000,0000,,还记得吗 在这里讲过
Dialogue: 0,0:03:59.17,0:04:03.56,Default,,0000,0000,0000,,哪些值与5之间的距离是10
Dialogue: 0,0:04:03.56,0:04:05.99,Default,,0000,0000,0000,,不管被5减的值是几
Dialogue: 0,0:04:05.99,0:04:08.56,Default,,0000,0000,0000,,它们与5之间的距离肯定是10
Dialogue: 0,0:04:08.56,0:04:09.52,Default,,0000,0000,0000,,这边呢
Dialogue: 0,0:04:09.52,0:04:13.08,Default,,0000,0000,0000,,哪些值与-2之间的距离是6
Dialogue: 0,0:04:13.08,0:04:15.51,Default,,0000,0000,0000,,那就是4 或-8
Dialogue: 0,0:04:15.51,0:04:17.96,Default,,0000,0000,0000,,自己试着验证下结果
Dialogue: 0,0:04:17.96,0:04:20.46,Default,,0000,0000,0000,,再做一个
Dialogue: 0,0:04:20.46,0:04:25.33,Default,,0000,0000,0000,,再来一个 这次用紫色
Dialogue: 0,0:04:25.33,0:04:30.19,Default,,0000,0000,0000,,这有4x的绝对值
Dialogue: 0,0:04:30.19,0:04:31.43,Default,,0000,0000,0000,,来计算一个有难度的
Dialogue: 0,0:04:31.43,0:04:33.39,Default,,0000,0000,0000,,4x减1
Dialogue: 0,0:04:33.39,0:04:36.58,Default,,0000,0000,0000,,4x-1的绝对值 等于--
Dialogue: 0,0:04:36.58,0:04:40.20,Default,,0000,0000,0000,,这里让它等于19
Dialogue: 0,0:04:40.20,0:04:41.77,Default,,0000,0000,0000,,这样 跟之前的解法一样
Dialogue: 0,0:04:41.77,0:04:47.64,Default,,0000,0000,0000,,一种情况是4x减1等于19
Dialogue: 0,0:04:47.64,0:04:51.67,Default,,0000,0000,0000,,另一种情况是4x减1等于-19
Dialogue: 0,0:04:51.67,0:04:53.13,Default,,0000,0000,0000,,因为当取绝对值以后
Dialogue: 0,0:04:53.13,0:04:54.80,Default,,0000,0000,0000,,都会得到19
Dialogue: 0,0:04:54.80,0:04:59.10,Default,,0000,0000,0000,,或者4x减1等于-19
Dialogue: 0,0:04:59.10,0:05:00.97,Default,,0000,0000,0000,,现在只需要解这两个方程式
Dialogue: 0,0:05:00.97,0:05:02.94,Default,,0000,0000,0000,,等式两边加1
Dialogue: 0,0:05:02.94,0:05:04.27,Default,,0000,0000,0000,,两个同时做
Dialogue: 0,0:05:04.27,0:05:08.51,Default,,0000,0000,0000,,两边加1后 得到4x等于20
Dialogue: 0,0:05:08.51,0:05:11.00,Default,,0000,0000,0000,,这两边加1后
Dialogue: 0,0:05:11.00,0:05:15.34,Default,,0000,0000,0000,,得到4x等于-18
Dialogue: 0,0:05:15.34,0:05:20.21,Default,,0000,0000,0000,,等式两边除4 得到x等于5
Dialogue: 0,0:05:20.21,0:05:23.92,Default,,0000,0000,0000,,这个等式两边除4 得到x等于-18/4
Dialogue: 0,0:05:23.92,0:05:31.77,Default,,0000,0000,0000,,也等于-9/2
Dialogue: 0,0:05:31.77,0:05:35.73,Default,,0000,0000,0000,,这两个x值同时满足这个绝对值方程式
Dialogue: 0,0:05:35.73,0:05:36.59,Default,,0000,0000,0000,,试试看
Dialogue: 0,0:05:36.59,0:05:39.58,Default,,0000,0000,0000,,-9/2乘4
Dialogue: 0,0:05:39.58,0:05:41.57,Default,,0000,0000,0000,,等于-18
Dialogue: 0,0:05:41.57,0:05:44.20,Default,,0000,0000,0000,,-18再减1就是-19
Dialogue: 0,0:05:44.20,0:05:46.74,Default,,0000,0000,0000,,取绝对值后 得到19
Dialogue: 0,0:05:46.74,0:05:49.92,Default,,0000,0000,0000,,等于5时 4乘5是20
Dialogue: 0,0:05:49.92,0:05:51.96,Default,,0000,0000,0000,,减1等于19
Dialogue: 0,0:05:51.96,0:05:53.26,Default,,0000,0000,0000,,再取绝对值以后
Dialogue: 0,0:05:53.26,0:05:55.92,Default,,0000,0000,0000,,还是等于19
Dialogue: 0,0:05:55.92,0:05:58.58,Default,,0000,0000,0000,,下面来画绝对值方程式的图形 增加趣味性
Dialogue: 0,0:05:58.58,0:05:59.28,Default,,0000,0000,0000,,现在有
Dialogue: 0,0:05:59.28,0:06:04.99,Default,,0000,0000,0000,,y等于x+3的绝对值
Dialogue: 0,0:06:04.99,0:06:07.84,Default,,0000,0000,0000,,这是个函数 或者说图形
Dialogue: 0,0:06:07.84,0:06:09.41,Default,,0000,0000,0000,,并包含绝对值在里面
Dialogue: 0,0:06:09.41,0:06:11.82,Default,,0000,0000,0000,,这要考虑两种情况
Dialogue: 0,0:06:11.82,0:06:13.14,Default,,0000,0000,0000,,一种情况是
Dialogue: 0,0:06:13.14,0:06:16.43,Default,,0000,0000,0000,,绝对值符号里的这个值为正
Dialogue: 0,0:06:16.43,0:06:18.87,Default,,0000,0000,0000,,也就是x+3
Dialogue: 0,0:06:18.87,0:06:23.42,Default,,0000,0000,0000,,写这边 x+3>0
Dialogue: 0,0:06:23.42,0:06:29.37,Default,,0000,0000,0000,,另一种情况是x+3<0
Dialogue: 0,0:06:29.37,0:06:32.66,Default,,0000,0000,0000,,当x+3>0时
Dialogue: 0,0:06:32.66,0:06:36.49,Default,,0000,0000,0000,,这个图形 或这条直线 这里可能还不能称为一条直线
Dialogue: 0,0:06:36.49,0:06:41.69,Default,,0000,0000,0000,,这个函数 就等同于y=x+3
Dialogue: 0,0:06:41.69,0:06:44.37,Default,,0000,0000,0000,,如果这边这个值是大于0的话
Dialogue: 0,0:06:44.37,0:06:46.75,Default,,0000,0000,0000,,那么绝对值符号就形同虚设
Dialogue: 0,0:06:46.75,0:06:48.78,Default,,0000,0000,0000,,那么这个就完全等同于
Dialogue: 0,0:06:48.78,0:06:50.28,Default,,0000,0000,0000,,y=x+3
Dialogue: 0,0:06:50.28,0:06:52.59,Default,,0000,0000,0000,,那么什么情况下x+3>0
Dialogue: 0,0:06:52.59,0:06:56.37,Default,,0000,0000,0000,,不等式两边减3
Dialogue: 0,0:06:56.37,0:06:59.91,Default,,0000,0000,0000,,得到x>-3
Dialogue: 0,0:06:59.91,0:07:02.25,Default,,0000,0000,0000,,那么当x>-3时
Dialogue: 0,0:07:02.25,0:07:08.46,Default,,0000,0000,0000,,这个图形与y=x+3是等同的
Dialogue: 0,0:07:08.46,0:07:11.50,Default,,0000,0000,0000,,当x+3<0时
Dialogue: 0,0:07:11.50,0:07:13.33,Default,,0000,0000,0000,,在这种情况下
Dialogue: 0,0:07:13.33,0:07:16.51,Default,,0000,0000,0000,,绝对值符号里的值为负
Dialogue: 0,0:07:16.51,0:07:20.36,Default,,0000,0000,0000,,在这种情况下等式就变成
Dialogue: 0,0:07:20.36,0:07:26.25,Default,,0000,0000,0000,,y等于-（x+3）
Dialogue: 0,0:07:26.25,0:07:27.54,Default,,0000,0000,0000,,为什么呢
Dialogue: 0,0:07:27.54,0:07:30.52,Default,,0000,0000,0000,,仔细听 现在这里是负值 如果
Dialogue: 0,0:07:30.52,0:07:33.06,Default,,0000,0000,0000,,x+3是负值
Dialogue: 0,0:07:33.06,0:07:36.01,Default,,0000,0000,0000,,在这个前提下 如果它是负值的话
Dialogue: 0,0:07:36.01,0:07:38.09,Default,,0000,0000,0000,,那么当取负值的绝对值后
Dialogue: 0,0:07:38.09,0:07:40.05,Default,,0000,0000,0000,,它肯定是得到正值
Dialogue: 0,0:07:40.05,0:07:43.28,Default,,0000,0000,0000,,就相当于把它与-1相乘
Dialogue: 0,0:07:43.28,0:07:45.87,Default,,0000,0000,0000,,如果知道是取负值的绝对值
Dialogue: 0,0:07:45.87,0:07:48.89,Default,,0000,0000,0000,,就相当于用这个值乘-1
Dialogue: 0,0:07:48.89,0:07:51.01,Default,,0000,0000,0000,,因为绝对值都是正值
Dialogue: 0,0:07:51.01,0:07:53.87,Default,,0000,0000,0000,,也就是这里所讨论的情况
Dialogue: 0,0:07:53.87,0:07:55.84,Default,,0000,0000,0000,,x+3小于0
Dialogue: 0,0:07:55.84,0:07:59.85,Default,,0000,0000,0000,,两边减3 当x小于-3
Dialogue: 0,0:07:59.85,0:08:01.28,Default,,0000,0000,0000,,当x小于-3
Dialogue: 0,0:08:01.28,0:08:03.92,Default,,0000,0000,0000,,那么当x<-3时
Dialogue: 0,0:08:03.92,0:08:05.04,Default,,0000,0000,0000,,图形应该是这样
Dialogue: 0,0:08:05.04,0:08:08.28,Default,,0000,0000,0000,,当x>-3
Dialogue: 0,0:08:08.28,0:08:09.60,Default,,0000,0000,0000,,图形是这样
Dialogue: 0,0:08:09.60,0:08:11.30,Default,,0000,0000,0000,,下面一起来看
Dialogue: 0,0:08:11.30,0:08:13.67,Default,,0000,0000,0000,,完整的图形
Dialogue: 0,0:08:13.67,0:08:21.52,Default,,0000,0000,0000,,先画数轴
Dialogue: 0,0:08:21.52,0:08:26.07,Default,,0000,0000,0000,,这是x轴 这是y轴
Dialogue: 0,0:08:26.07,0:08:29.09,Default,,0000,0000,0000,,先把这个函数乘出来 这样可以得到mx
Dialogue: 0,0:08:29.09,0:08:29.87,Default,,0000,0000,0000,,加b的函数格式
Dialogue: 0,0:08:29.87,0:08:36.07,Default,,0000,0000,0000,,这个等于-x-3
Dialogue: 0,0:08:36.07,0:08:37.41,Default,,0000,0000,0000,,先看看这种函数图形
Dialogue: 0,0:08:37.41,0:08:38.62,Default,,0000,0000,0000,,的一般形式
Dialogue: 0,0:08:38.62,0:08:42.02,Default,,0000,0000,0000,,-x-3
Dialogue: 0,0:08:42.02,0:08:47.38,Default,,0000,0000,0000,,y轴截距是-3 所以1 2 3
Dialogue: 0,0:08:47.38,0:08:51.06,Default,,0000,0000,0000,,-x那就应该是向下倾斜 也就是
Dialogue: 0,0:08:51.06,0:08:52.29,Default,,0000,0000,0000,,向下斜率为1
Dialogue: 0,0:08:52.29,0:08:53.54,Default,,0000,0000,0000,,看起来就是这样
Dialogue: 0,0:08:56.84,0:09:02.83,Default,,0000,0000,0000,,x轴的截距应该是x等于
Dialogue: 0,0:09:02.83,0:09:07.74,Default,,0000,0000,0000,,当假设y等于0时 这边x
Dialogue: 0,0:09:07.74,0:09:08.58,Default,,0000,0000,0000,,等于-3
Dialogue: 0,0:09:08.58,0:09:10.38,Default,,0000,0000,0000,,穿过这条线
Dialogue: 0,0:09:10.38,0:09:11.92,Default,,0000,0000,0000,,这个点
Dialogue: 0,0:09:11.92,0:09:14.19,Default,,0000,0000,0000,,这个图形 如果没有这里这个限制条件
Dialogue: 0,0:09:14.19,0:09:15.60,Default,,0000,0000,0000,,应该是这样
Dialogue: 0,0:09:19.89,0:09:22.76,Default,,0000,0000,0000,,如果没有区间限制条件
Dialogue: 0,0:09:22.76,0:09:23.88,Default,,0000,0000,0000,,x轴的这个区间限制条件
Dialogue: 0,0:09:23.88,0:09:27.08,Default,,0000,0000,0000,,那么这个图形 应该是怎样的
Dialogue: 0,0:09:27.08,0:09:27.48,Default,,0000,0000,0000,,来看看
Dialogue: 0,0:09:27.48,0:09:31.81,Default,,0000,0000,0000,,y轴截距是3
Dialogue: 0,0:09:31.81,0:09:33.23,Default,,0000,0000,0000,,像这样
Dialogue: 0,0:09:33.23,0:09:35.26,Default,,0000,0000,0000,,x轴的截距呢
Dialogue: 0,0:09:35.26,0:09:37.97,Default,,0000,0000,0000,,当y等于0时 x等于-3
Dialogue: 0,0:09:37.97,0:09:39.76,Default,,0000,0000,0000,,还是一样穿过这个点
Dialogue: 0,0:09:39.76,0:09:40.62,Default,,0000,0000,0000,,斜率为1
Dialogue: 0,0:09:40.62,0:09:43.71,Default,,0000,0000,0000,,那就应该是这样的
Dialogue: 0,0:09:43.71,0:09:45.33,Default,,0000,0000,0000,,这就是这个函数的图形
Dialogue: 0,0:09:45.33,0:09:48.10,Default,,0000,0000,0000,,现在 可以得出结论 绝对值
Dialogue: 0,0:09:48.10,0:09:52.03,Default,,0000,0000,0000,,函数为紫色直线
Dialogue: 0,0:09:52.03,0:09:53.83,Default,,0000,0000,0000,,当x<-3时
Dialogue: 0,0:09:53.83,0:09:57.07,Default,,0000,0000,0000,,当x<-3 这里是x等于
Dialogue: 0,0:09:57.07,0:09:59.59,Default,,0000,0000,0000,,-3 当x<-3
Dialogue: 0,0:09:59.59,0:10:03.17,Default,,0000,0000,0000,,它就是这条紫线
Dialogue: 0,0:10:03.17,0:10:04.57,Default,,0000,0000,0000,,就是这条
Dialogue: 0,0:10:04.57,0:10:07.39,Default,,0000,0000,0000,,上面是当x<-3时的图形
Dialogue: 0,0:10:07.39,0:10:10.83,Default,,0000,0000,0000,,但是如果x>-3时 就应该是
Dialogue: 0,0:10:10.83,0:10:12.16,Default,,0000,0000,0000,,这条绿线了
Dialogue: 0,0:10:12.16,0:10:14.64,Default,,0000,0000,0000,,就是这条
Dialogue: 0,0:10:14.64,0:10:17.48,Default,,0000,0000,0000,,图形看起来很像奇怪的V
Dialogue: 0,0:10:17.48,0:10:21.43,Default,,0000,0000,0000,,当x>-3时 应该是正值
Dialogue: 0,0:10:21.43,0:10:24.95,Default,,0000,0000,0000,,所以这个图形 斜率为正
Dialogue: 0,0:10:24.95,0:10:28.27,Default,,0000,0000,0000,,但当x<-3时 本质上
Dialogue: 0,0:10:28.27,0:10:30.55,Default,,0000,0000,0000,,其实是取这个函数的负值 如果想要
Dialogue: 0,0:10:30.55,0:10:32.28,Default,,0000,0000,0000,,这么理解的话 所以这里是负斜率
Dialogue: 0,0:10:32.28,0:10:35.06,Default,,0000,0000,0000,,如果看到这种V型函数 或是
Dialogue: 0,0:10:35.06,0:10:38.25,Default,,0000,0000,0000,,V型图 那就表明它是
Dialogue: 0,0:10:38.25,0:10:39.95,Default,,0000,0000,0000,,绝对值函数