Lecture two absolute value
Example 1
∙In a PE lesson, the teacher organized a game. as shown in the figure
Four students standing on the circle, Who first arrived at the center of the circle ?
question 1 Is the distance which from four students to the center the same?
question 2 will their direction affect the length of the distance ?
conclusion Has nothing to do with direction, equal distance
1, the concept about absolute value : The number a which show a point on the number axis and the distance from the origin is called the absolute value of a. express to be |a|
2 Exercise
|+2| = |-3| = |1/5| =
The absolute value of a general law:
1: The absolute value of zero is zero
2 The absolute value of a negative number is its opposite
3 The absolute value of a positive number is itself
Mean：①if a＞0，then |a|=a； ②if a＜0，then |a|=–a；
③if a=0，then |a|=0；
or：。
Homework
Exercise 1:find the value of the following
(3)a(a＜0)； (4)3b(b＞0)；
(5)a－2(a＜2)； (6)a－b．
Exercise 2: decide Whether all of the following is correct (Right into the "T", Error into the "F")
(1)｜－a｜＝｜a｜； ( )
(2)－｜a｜＝｜－a｜； ( )
(4)if ｜a｜＝｜b｜，then a＝b； ( )
(5)if a＝b， then ｜a｜＝｜b｜； ( )
(6)if ｜a｜＞｜b｜，then a＞b； ( )
高苏宁
(7)if a＞b， then ｜a｜＞｜b｜； ( )
(8)if a＞b，then ｜b－a｜＝a－b． ( )
Exercise 3:T or F (判断对错)
(1) If the opposite of a number is itself, the number is 0． ( )
(2) If the reciprocal of a number is itself, this number is 1 and 0 ． ( )
(3)cd激光头 If the absolute value of a number is itself, then the number is 0 or 1． ( )
(4) If the absolute value of a number is its opposite, so the number is negative． ( )
Exercise 4 if (a－1)2＋｜b＋3｜＝0， find the value of a、b．
Exercise 5 Compare the size of the following number in each group，Fill in the proper relationship between symbols on horizontal line
(“＜”“＝”“＞”)
(1)｜－0.01｜______－｜100｜；
(2)－(－3)______－｜－3｜；
(3)－[－(－90)]_______0；
(4)if a＜3，a－3______0；｜3－a｜______a－3．
Exercise 6
豫公网安备41160202000603
站长QQ:729038198
关于我们
投诉建议