Junior high school mathematics important kaodian
Number axis: the straight line defining the origin, positive direction and unit length is called number axis (when drawing number axis, it should be noted that the above three elements are indispensable).
When solving problems, we should really master the idea of combining numbers with shapes, understand the one-to-one correspondence between real numbers and points on the number axis, and use them flexibly.
(1) Draw a horizontal straight line, take a point on the straight line to represent 0 (origin), choose a certain length as the unit length, and specify the right direction on the straight line as the positive direction to get the number axis ("three elements").
② Any rational number can be represented by a point on the number axis.
(3) If two numbers differ only in sign, then we call one of them the inverse of the other number, and we also call these two numbers the inverse of each other.
Function: a. Visually compare the sizes of real numbers; B. clearly reflect the absolute value; C. establish a one-to-one correspondence between points and real numbers.
5. Inverse number
Operation of mathematical rational numbers
Addition: ① Add the same sign, take the same sign, and add the absolute values. ② When the absolute values are equal, the sum of different symbols is 0; When the absolute values are not equal, take the sign of the number with the larger absolute value and subtract the smaller absolute value from the larger absolute value. (3) A number and 0 add up unchanged.
Subtraction: Subtracting a number equals adding the reciprocal of this number.
Multiplication: ① Multiplication of two numbers, positive sign of the same sign, negative sign of different sign, absolute value. ② Multiply any number by 0 to get 0. ③ Two rational numbers whose product is 1 are reciprocal.
Division: ① Dividing by a number equals multiplying the reciprocal of a number. ②0 is not divisible.
Power: the operation of finding the product of n identical factors A is called power, the result of power is called power, A is called base, and N is called degree.
Solution of quadratic equation in junior high school mathematics
① direct Kaiping method
Using the definition of square root to find the solution of quadratic equation in one variable is called direct Kaiping method. The direct Kaiping method is suitable for solving quadratic equations with one variable. According to the definition of square root, it is the square root of b, when B < 0, the equation has no real root.
(2) Matching method
Matching method is an important mathematical method, which is not only suitable for solving quadratic equations with one variable, but also widely used in other fields of mathematics. The theoretical basis of the matching method is the complete square formula. If a in the formula is regarded as an unknown x and replaced by x, there is.
③ Formula method
Formula method is a method to solve the quadratic equation of one variable by finding the root formula, and it is a general method to solve the quadratic equation of one variable.
The above is my summary of junior high school mathematics knowledge points for your reference only, and I hope it will help you.