文档介绍：北师大版《数学》(八年级下册)知识点总结(Beijing Normal
University Edition Mathematics (grade eight) summarizes
knowledge)
Beijing Normalnt two real or unsplit)
Generally:
If a>b, then A-B is positive: conversely, if A-B is positive, then a>b:
If a=b, then A-B is equal to 0; conversely, if A-B equals 0, then a=b;
If a<b, then A-B is negative; conversely, if A-B is positive, then a<b:
That is:
A>b a~b>0
<===>
A=b a~b=O
<===>
A<b a~b<0
<===>
This shows that to compare the size of two real numbers, it is possible to look at their differences
three
Solution sets of inequalities:
You can make 1. inequalities for the value of the unknown, called inequalities: all solutions of an inequality,
The solution set consisting of this inequality; the process of finding the solution set of inequalities is called solving inequality
You can have an unlimited number of solutions of 2. inequalities, is within the scope of a certain number of all, and the equation
Differential interpretation
Set in the solution on the following 3. axis inequality:
With the axis said solution set of inequalities, to determine the boundary and direction:
Boundary: an equal sign is a solid circle, without equals is a hollow circle:
Direction: big right, small left
Four. One yuan once inequality:
The 1. contains only one unknown, with unknown formula is the number of unknowns is 1. type, like this
The inequality of a kind is called a unary inequality
2. yuan for a solution of inequality process and solving a linear equation, in particular, when ranging
When both sides are multiplied by a negative number, the inequality sign changes direction
The 3. one yuan a step of inequality:
Go to the denominator;
Parentheses;
The transposition;
The merger of similar items:
Change coefficient to 1 (change of inequality)
4. a basic situation of ax>b inequality (or ax<b)
When a>0, the solution is a
B
X>;
When a=0, and b<0, then x takes all real numbers:
When a=0 and B is not less than 0, there is