[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,,讓我們來學習解絕對值方程式
Dialogue: 0,0:00:03.88,0:00:05.12,Default,,0000,0000,0000,,先來複習下
Dialogue: 0,0:00:05.12,0:00:07.65,Default,,0000,0000,0000,,當計算一個數值的絕對值時
Dialogue: 0,0:00:07.65,0:00:10.68,Default,,0000,0000,0000,,以-1爲例 來計算絕對值
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,,計算出1與0之間的距離
Dialogue: 0,0:00:16.09,0:00:20.62,Default,,0000,0000,0000,,對-1來說 下面以數軸示例
Dialogue: 0,0:00:20.62,0:00:23.31,Default,,0000,0000,0000,,這個沒畫好
Dialogue: 0,0:00:23.31,0:00:26.23,Default,,0000,0000,0000,,這是數軸 這是0
Dialogue: 0,0:00:26.23,0:00:28.47,Default,,0000,0000,0000,,這是-1
Dialogue: 0,0:00:28.47,0:00:30.23,Default,,0000,0000,0000,,-1與0之間的距離是1
Dialogue: 0,0:00:30.23,0:00:33.25,Default,,0000,0000,0000,,那-1的絕對值就是1
Dialogue: 0,0:00:33.25,0:00:38.85,Default,,0000,0000,0000,,1和0之間的距離也是1
Dialogue: 0,0:00:38.85,0:00:40.61,Default,,0000,0000,0000,,所以1的絕對值同樣是1
Dialogue: 0,0:00:40.61,0:00:43.50,Default,,0000,0000,0000,,也就是說 絕對值爲與0之間的距離
Dialogue: 0,0:00:43.50,0:00:45.59,Default,,0000,0000,0000,,來換一種更簡單的方式來理解
Dialogue: 0,0:00:45.59,0:00:48.60,Default,,0000,0000,0000,,絕對值其實就是取數值的正值
Dialogue: 0,0:00:48.60,0:00:59.36,Default,,0000,0000,0000,,-7346的絕對值是7346.
Dialogue: 0,0:00:59.36,0:01:00.78,Default,,0000,0000,0000,,理解這點以後 下面
Dialogue: 0,0:01:00.78,0:01:05.05,Default,,0000,0000,0000,,開始學習解絕對值方程式
Dialogue: 0,0:01:05.05,0:01:06.68,Default,,0000,0000,0000,,來看這個方程式
Dialogue: 0,0:01:06.68,0:01:14.50,Default,,0000,0000,0000,,x-5的絕對值等於10
Dialogue: 0,0:01:14.50,0:01:15.90,Default,,0000,0000,0000,,可以這樣解讀這個等式
Dialogue: 0,0:01:15.90,0:01:18.16,Default,,0000,0000,0000,,也希望能夠這樣理解 這就是說
Dialogue: 0,0:01:18.16,0:01:23.12,Default,,0000,0000,0000,,x與5之間的距離爲10
Dialogue: 0,0:01:23.12,0:01:26.75,Default,,0000,0000,0000,,與5之間的距離是10的數值有幾個
Dialogue: 0,0:01:26.75,0:01:29.43,Default,,0000,0000,0000,,大家應該已經想到解法了
Dialogue: 0,0:01:29.43,0:01:31.96,Default,,0000,0000,0000,,不過下面要學習更係統的解法
Dialogue: 0,0:01:31.96,0:01:36.51,Default,,0000,0000,0000,,這個方程式有兩種情況
Dialogue: 0,0:01:36.51,0:01:41.80,Default,,0000,0000,0000,,一種是x-5等於10
Dialogue: 0,0:01:41.80,0:01:44.63,Default,,0000,0000,0000,,如果假定絕對值裏面的值爲10
Dialogue: 0,0:01:44.63,0:01:46.61,Default,,0000,0000,0000,,取絕對值後
Dialogue: 0,0:01:46.61,0:01:48.38,Default,,0000,0000,0000,,會得到10
Dialogue: 0,0:01:48.38,0:01:53.13,Default,,0000,0000,0000,,或者假設x-5等於-10
Dialogue: 0,0:01:53.13,0:01:58.70,Default,,0000,0000,0000,,如果x-5等於-10 取絕對值後
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,,所以第二種情況是 x-5等於-10
Dialogue: 0,0:02:04.28,0:02:07.73,Default,,0000,0000,0000,,兩種情況同時滿足這個方程式
Dialogue: 0,0:02:07.73,0:02:08.96,Default,,0000,0000,0000,,先解這個
Dialogue: 0,0:02:08.96,0:02:11.50,Default,,0000,0000,0000,,等式兩邊加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,,再解這個 等式兩邊加5
Dialogue: 0,0:02:17.83,0:02:20.90,Default,,0000,0000,0000,,x等於-5
Dialogue: 0,0:02:20.90,0:02:21.96,Default,,0000,0000,0000,,得出計算結果
Dialogue: 0,0:02:21.96,0:02:24.91,Default,,0000,0000,0000,,有兩個x值滿足這個方程式
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等於10 取絕對值後
Dialogue: 0,0:02:29.50,0:02:32.69,Default,,0000,0000,0000,,得到10 或者x爲-5
Dialogue: 0,0:02:32.69,0:02:36.06,Default,,0000,0000,0000,,-5減5等於-10
Dialogue: 0,0:02:36.06,0:02:39.02,Default,,0000,0000,0000,,取絕對值後 還是10
Dialogue: 0,0:02:39.02,0:02:41.63,Default,,0000,0000,0000,,注意 這兩個值
Dialogue: 0,0:02:41.63,0:02:45.75,Default,,0000,0000,0000,,與5之間的距離都是10
Dialogue: 0,0:02:45.75,0:02:48.05,Default,,0000,0000,0000,,再解一個
Dialogue: 0,0:02:48.05,0:02:51.13,Default,,0000,0000,0000,,再來一個
Dialogue: 0,0:02:51.13,0:02:52.18,Default,,0000,0000,0000,,現在有
Dialogue: 0,0:02:52.18,0:02:58.58,Default,,0000,0000,0000,,x+2的絕對值等於6
Dialogue: 0,0:02:58.58,0:02:59.61,Default,,0000,0000,0000,,這說明什麽呢
Dialogue: 0,0:02:59.61,0:03:03.13,Default,,0000,0000,0000,,也就是說 要麽x+2
Dialogue: 0,0:03:03.13,0:03:07.03,Default,,0000,0000,0000,,也就是絕對值符號裏的這個值 它等於6
Dialogue: 0,0:03:07.03,0:03:10.38,Default,,0000,0000,0000,,或者絕對值符號裏的這個值
Dialogue: 0,0:03:10.38,0:03:12.05,Default,,0000,0000,0000,,x+2 它等於-6
Dialogue: 0,0:03:12.05,0:03:13.91,Default,,0000,0000,0000,,假設等於-6時
Dialogue: 0,0:03:13.91,0:03:16.21,Default,,0000,0000,0000,,取絕對值後 得到6
Dialogue: 0,0:03:16.21,0:03:20.34,Default,,0000,0000,0000,,那麽 假設x+2等於-6
Dialogue: 0,0:03:20.34,0:03:22.88,Default,,0000,0000,0000,,然後 等式兩邊減2
Dialogue: 0,0:03:22.88,0:03:25.85,Default,,0000,0000,0000,,得到 x等於4
Dialogue: 0,0:03:25.85,0:03:29.78,Default,,0000,0000,0000,,再看這個方程式 兩邊減2
Dialogue: 0,0:03:29.78,0:03:33.69,Default,,0000,0000,0000,,得到x等於-8
Dialogue: 0,0:03:33.69,0:03:37.24,Default,,0000,0000,0000,,這就是方程式的兩種解法
Dialogue: 0,0:03:37.24,0:03:39.74,Default,,0000,0000,0000,,爲了加深理解
Dialogue: 0,0:03:39.74,0:03:42.50,Default,,0000,0000,0000,,對於絕對值 可以把它看成是距離
Dialogue: 0,0:03:42.50,0:03:43.94,Default,,0000,0000,0000,,這樣重寫這個絕對值方程式
Dialogue: 0,0:03:43.94,0:03:50.41,Default,,0000,0000,0000,,x減-2的絕對值等於6
Dialogue: 0,0:03:50.41,0:03:52.76,Default,,0000,0000,0000,,其實就是說
Dialogue: 0,0:03:52.76,0:03:57.59,Default,,0000,0000,0000,,哪些值與-2之間的距離剛好是6呢
Dialogue: 0,0:03:57.59,0:03:59.17,Default,,0000,0000,0000,,還記得嗎 在這裡講過
Dialogue: 0,0:03:59.17,0:04:03.56,Default,,0000,0000,0000,,哪些值與5之間的距離是10
Dialogue: 0,0:04:03.56,0:04:05.99,Default,,0000,0000,0000,,不管被5減的值是幾
Dialogue: 0,0:04:05.99,0:04:08.56,Default,,0000,0000,0000,,它們與5之間的距離肯定是10
Dialogue: 0,0:04:08.56,0:04:09.52,Default,,0000,0000,0000,,這邊呢
Dialogue: 0,0:04:09.52,0:04:13.08,Default,,0000,0000,0000,,哪些值與-2之間的距離是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,,自己試著驗證下結果
Dialogue: 0,0:04:17.96,0:04:20.46,Default,,0000,0000,0000,,再做一個
Dialogue: 0,0:04:20.46,0:04:25.33,Default,,0000,0000,0000,,再來一個 這次用紫色
Dialogue: 0,0:04:25.33,0:04:30.19,Default,,0000,0000,0000,,這有4x的絕對值
Dialogue: 0,0:04:30.19,0:04:31.43,Default,,0000,0000,0000,,來計算一個有難度的
Dialogue: 0,0:04:31.43,0:04:33.39,Default,,0000,0000,0000,,4x減1
Dialogue: 0,0:04:33.39,0:04:36.58,Default,,0000,0000,0000,,4x-1的絕對值 等於--
Dialogue: 0,0:04:36.58,0:04:40.20,Default,,0000,0000,0000,,這裡讓它等於19
Dialogue: 0,0:04:40.20,0:04:41.77,Default,,0000,0000,0000,,這樣 跟之前的解法一樣
Dialogue: 0,0:04:41.77,0:04:47.64,Default,,0000,0000,0000,,一種情況是4x減1等於19
Dialogue: 0,0:04:47.64,0:04:51.67,Default,,0000,0000,0000,,另一種情況是4x減1等於-19
Dialogue: 0,0:04:51.67,0:04:53.13,Default,,0000,0000,0000,,因爲當取絕對值以後
Dialogue: 0,0:04:53.13,0:04:54.80,Default,,0000,0000,0000,,都會得到19
Dialogue: 0,0:04:54.80,0:04:59.10,Default,,0000,0000,0000,,或者4x減1等於-19
Dialogue: 0,0:04:59.10,0:05:00.97,Default,,0000,0000,0000,,現在只需要解這兩個方程式
Dialogue: 0,0:05:00.97,0:05:02.94,Default,,0000,0000,0000,,等式兩邊加1
Dialogue: 0,0:05:02.94,0:05:04.27,Default,,0000,0000,0000,,兩個同時做
Dialogue: 0,0:05:04.27,0:05:08.51,Default,,0000,0000,0000,,兩邊加1後 得到4x等於20
Dialogue: 0,0:05:08.51,0:05:11.00,Default,,0000,0000,0000,,這兩邊加1後
Dialogue: 0,0:05:11.00,0:05:15.34,Default,,0000,0000,0000,,得到4x等於-18
Dialogue: 0,0:05:15.34,0:05:20.21,Default,,0000,0000,0000,,等式兩邊除4 得到x等於5
Dialogue: 0,0:05:20.21,0:05:23.92,Default,,0000,0000,0000,,這個等式兩邊除4 得到x等於-18/4
Dialogue: 0,0:05:23.92,0:05:31.77,Default,,0000,0000,0000,,也等於-9/2
Dialogue: 0,0:05:31.77,0:05:35.73,Default,,0000,0000,0000,,這兩個x值同時滿足這個絕對值方程式
Dialogue: 0,0:05:35.73,0:05:36.59,Default,,0000,0000,0000,,試試看
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,,等於-18
Dialogue: 0,0:05:41.57,0:05:44.20,Default,,0000,0000,0000,,-18再減1就是-19
Dialogue: 0,0:05:44.20,0:05:46.74,Default,,0000,0000,0000,,取絕對值後 得到19
Dialogue: 0,0:05:46.74,0:05:49.92,Default,,0000,0000,0000,,等於5時 4乘5是20
Dialogue: 0,0:05:49.92,0:05:51.96,Default,,0000,0000,0000,,減1等於19
Dialogue: 0,0:05:51.96,0:05:53.26,Default,,0000,0000,0000,,再取絕對值以後
Dialogue: 0,0:05:53.26,0:05:55.92,Default,,0000,0000,0000,,還是等於19
Dialogue: 0,0:05:55.92,0:05:58.58,Default,,0000,0000,0000,,下面來畫絕對值方程式的圖形 增加趣味性
Dialogue: 0,0:05:58.58,0:05:59.28,Default,,0000,0000,0000,,現在有
Dialogue: 0,0:05:59.28,0:06:04.99,Default,,0000,0000,0000,,y等於x+3的絕對值
Dialogue: 0,0:06:04.99,0:06:07.84,Default,,0000,0000,0000,,這是個函數 或者說圖形
Dialogue: 0,0:06:07.84,0:06:09.41,Default,,0000,0000,0000,,並包含絕對值在裏面
Dialogue: 0,0:06:09.41,0:06:11.82,Default,,0000,0000,0000,,這要考慮兩種情況
Dialogue: 0,0:06:11.82,0:06:13.14,Default,,0000,0000,0000,,一種情況是
Dialogue: 0,0:06:13.14,0:06:16.43,Default,,0000,0000,0000,,絕對值符號裏的這個值爲正
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,,寫這邊 x+3>0
Dialogue: 0,0:06:23.42,0:06:29.37,Default,,0000,0000,0000,,另一種情況是x+3<0
Dialogue: 0,0:06:29.37,0:06:32.66,Default,,0000,0000,0000,,當x+3>0時
Dialogue: 0,0:06:32.66,0:06:36.49,Default,,0000,0000,0000,,這個圖形 或這條直線 這裡可能還不能稱爲一條直線
Dialogue: 0,0:06:36.49,0:06:41.69,Default,,0000,0000,0000,,這個函數 就等同於y=x+3
Dialogue: 0,0:06:41.69,0:06:44.37,Default,,0000,0000,0000,,如果這邊這個值是大於0的話
Dialogue: 0,0:06:44.37,0:06:46.75,Default,,0000,0000,0000,,那麽絕對值符號就形同虛設
Dialogue: 0,0:06:46.75,0:06:48.78,Default,,0000,0000,0000,,那麽這個就完全等同於
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,,那麽什麽情況下x+3>0
Dialogue: 0,0:06:52.59,0:06:56.37,Default,,0000,0000,0000,,不等式兩邊減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,,那麽當x>-3時
Dialogue: 0,0:07:02.25,0:07:08.46,Default,,0000,0000,0000,,這個圖形與y=x+3是等同的
Dialogue: 0,0:07:08.46,0:07:11.50,Default,,0000,0000,0000,,當x+3<0時
Dialogue: 0,0:07:11.50,0:07:13.33,Default,,0000,0000,0000,,在這種情況下
Dialogue: 0,0:07:13.33,0:07:16.51,Default,,0000,0000,0000,,絕對值符號裏的值爲負
Dialogue: 0,0:07:16.51,0:07:20.36,Default,,0000,0000,0000,,在這種情況下等式就變成
Dialogue: 0,0:07:20.36,0:07:26.25,Default,,0000,0000,0000,,y等於-（x+3）
Dialogue: 0,0:07:26.25,0:07:27.54,Default,,0000,0000,0000,,爲什麽呢
Dialogue: 0,0:07:27.54,0:07:30.52,Default,,0000,0000,0000,,仔細聽 現在這裡是負值 如果
Dialogue: 0,0:07:30.52,0:07:33.06,Default,,0000,0000,0000,,x+3是負值
Dialogue: 0,0:07:33.06,0:07:36.01,Default,,0000,0000,0000,,在這個前提下 如果它是負值的話
Dialogue: 0,0:07:36.01,0:07:38.09,Default,,0000,0000,0000,,那麽當取負值的絕對值後
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,,就相當於把它與-1相乘
Dialogue: 0,0:07:43.28,0:07:45.87,Default,,0000,0000,0000,,如果知道是取負值的絕對值
Dialogue: 0,0:07:45.87,0:07:48.89,Default,,0000,0000,0000,,就相當於用這個值乘-1
Dialogue: 0,0:07:48.89,0:07:51.01,Default,,0000,0000,0000,,因爲絕對值都是正值
Dialogue: 0,0:07:51.01,0:07:53.87,Default,,0000,0000,0000,,也就是這裡所討論的情況
Dialogue: 0,0:07:53.87,0:07:55.84,Default,,0000,0000,0000,,x+3少於0
Dialogue: 0,0:07:55.84,0:07:59.85,Default,,0000,0000,0000,,兩邊減3 當x少於-3
Dialogue: 0,0:07:59.85,0:08:01.28,Default,,0000,0000,0000,,當x少於-3
Dialogue: 0,0:08:01.28,0:08:03.92,Default,,0000,0000,0000,,那麽當x<-3時
Dialogue: 0,0:08:03.92,0:08:05.04,Default,,0000,0000,0000,,圖形應該是這樣
Dialogue: 0,0:08:05.04,0:08:08.28,Default,,0000,0000,0000,,當x>-3
Dialogue: 0,0:08:08.28,0:08:09.60,Default,,0000,0000,0000,,圖形是這樣
Dialogue: 0,0:08:09.60,0:08:11.30,Default,,0000,0000,0000,,下面一起來看
Dialogue: 0,0:08:11.30,0:08:13.67,Default,,0000,0000,0000,,完整的圖形
Dialogue: 0,0:08:13.67,0:08:21.52,Default,,0000,0000,0000,,先畫數軸
Dialogue: 0,0:08:21.52,0:08:26.07,Default,,0000,0000,0000,,這是x軸 這是y軸
Dialogue: 0,0:08:26.07,0:08:29.09,Default,,0000,0000,0000,,先把這個函數乘出來 這樣可以得到mx
Dialogue: 0,0:08:29.09,0:08:29.87,Default,,0000,0000,0000,,加b的函數格式
Dialogue: 0,0:08:29.87,0:08:36.07,Default,,0000,0000,0000,,這個等於-x-3
Dialogue: 0,0:08:36.07,0:08:37.41,Default,,0000,0000,0000,,先看看這種函數圖形
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軸截距是-3 所以1 2 3
Dialogue: 0,0:08:47.38,0:08:51.06,Default,,0000,0000,0000,,-x那就應該是向下傾斜 也就是
Dialogue: 0,0:08:51.06,0:08:52.29,Default,,0000,0000,0000,,向下斜率爲1
Dialogue: 0,0:08:52.29,0:08:53.54,Default,,0000,0000,0000,,看起來就是這樣
Dialogue: 0,0:08:56.84,0:09:02.83,Default,,0000,0000,0000,,x軸的截距應該是x等於
Dialogue: 0,0:09:02.83,0:09:07.74,Default,,0000,0000,0000,,當假設y等於0時 這邊x
Dialogue: 0,0:09:07.74,0:09:08.58,Default,,0000,0000,0000,,等於-3
Dialogue: 0,0:09:08.58,0:09:10.38,Default,,0000,0000,0000,,穿過這條線
Dialogue: 0,0:09:10.38,0:09:11.92,Default,,0000,0000,0000,,這個點
Dialogue: 0,0:09:11.92,0:09:14.19,Default,,0000,0000,0000,,這個圖形 如果沒有這裡這個限制條件
Dialogue: 0,0:09:14.19,0:09:15.60,Default,,0000,0000,0000,,應該是這樣
Dialogue: 0,0:09:19.89,0:09:22.76,Default,,0000,0000,0000,,如果沒有區間限制條件
Dialogue: 0,0:09:22.76,0:09:23.88,Default,,0000,0000,0000,,x軸的這個區間限制條件
Dialogue: 0,0:09:23.88,0:09:27.08,Default,,0000,0000,0000,,那麽這個圖形 應該是怎樣的
Dialogue: 0,0:09:27.08,0:09:27.48,Default,,0000,0000,0000,,來看看
Dialogue: 0,0:09:27.48,0:09:31.81,Default,,0000,0000,0000,,y軸截距是3
Dialogue: 0,0:09:31.81,0:09:33.23,Default,,0000,0000,0000,,像這樣
Dialogue: 0,0:09:33.23,0:09:35.26,Default,,0000,0000,0000,,x軸的截距呢
Dialogue: 0,0:09:35.26,0:09:37.97,Default,,0000,0000,0000,,當y等於0時 x等於-3
Dialogue: 0,0:09:37.97,0:09:39.76,Default,,0000,0000,0000,,還是一樣穿過這個點
Dialogue: 0,0:09:39.76,0:09:40.62,Default,,0000,0000,0000,,斜率爲1
Dialogue: 0,0:09:40.62,0:09:43.71,Default,,0000,0000,0000,,那就應該是這樣的
Dialogue: 0,0:09:43.71,0:09:45.33,Default,,0000,0000,0000,,這就是這個函數的圖形
Dialogue: 0,0:09:45.33,0:09:48.10,Default,,0000,0000,0000,,現在 可以得出結論 絕對值
Dialogue: 0,0:09:48.10,0:09:52.03,Default,,0000,0000,0000,,函數爲紫色直線
Dialogue: 0,0:09:52.03,0:09:53.83,Default,,0000,0000,0000,,當x<-3時
Dialogue: 0,0:09:53.83,0:09:57.07,Default,,0000,0000,0000,,當x<-3 這裡是x等於
Dialogue: 0,0:09:57.07,0:09:59.59,Default,,0000,0000,0000,,-3 當x<-3
Dialogue: 0,0:09:59.59,0:10:03.17,Default,,0000,0000,0000,,它就是這條紫線
Dialogue: 0,0:10:03.17,0:10:04.57,Default,,0000,0000,0000,,就是這條
Dialogue: 0,0:10:04.57,0:10:07.39,Default,,0000,0000,0000,,上面是當x<-3時的圖形
Dialogue: 0,0:10:07.39,0:10:10.83,Default,,0000,0000,0000,,但是如果x>-3時 就應該是
Dialogue: 0,0:10:10.83,0:10:12.16,Default,,0000,0000,0000,,這條綠線了
Dialogue: 0,0:10:12.16,0:10:14.64,Default,,0000,0000,0000,,就是這條
Dialogue: 0,0:10:14.64,0:10:17.48,Default,,0000,0000,0000,,圖形看起來很像奇怪的V
Dialogue: 0,0:10:17.48,0:10:21.43,Default,,0000,0000,0000,,當x>-3時 應該是正值
Dialogue: 0,0:10:21.43,0:10:24.95,Default,,0000,0000,0000,,所以這個圖形 斜率爲正
Dialogue: 0,0:10:24.95,0:10:28.27,Default,,0000,0000,0000,,但當x<-3時 本質上
Dialogue: 0,0:10:28.27,0:10:30.55,Default,,0000,0000,0000,,其實是取這個函數的負值 如果想要
Dialogue: 0,0:10:30.55,0:10:32.28,Default,,0000,0000,0000,,這麽理解的話 所以這裡是負斜率
Dialogue: 0,0:10:32.28,0:10:35.06,Default,,0000,0000,0000,,如果看到這種V型函數 或是
Dialogue: 0,0:10:35.06,0:10:38.25,Default,,0000,0000,0000,,V型圖 那就表明它是
Dialogue: 0,0:10:38.25,0:10:39.95,Default,,0000,0000,0000,,絕對值函數