Seek 20 knowledge points of each subject in the third year of junior high school, and summarize the

Sorting out the error-prone knowledge points of mathematics in the third year of junior high school.

1. The relevant concepts of rational numbers, irrational numbers and real numbers are misunderstood, and the meaning concepts of opposite numbers, reciprocal numbers and absolute values are confused. I can't figure out the classification of absolute values and numbers. There are more multiple-choice questions.

2. Regarding the operation of real numbers, it is necessary to grasp the relevant concepts and properties of real numbers, and flexibly use various operation laws, the key is to control the symbols; In more complex operations, the order of operations is not paid attention to or the laws of operation are not used reasonably, resulting in errors in operations.

3. The difference between square root, arithmetic square root, and cubic root.

4. When the fractional value is zero, it is easy to ignore that the denominator cannot be zero.

5. Pay attention to the changes in the algorithm and symbols in fractional operations. When the numerator and denominator of the fraction is a polynomial, the factorization should be factored first, and the factorization should be decomposed until it can no longer be decomposed. Fill-in-the-blank questions are easy to test.

Common test points with similar triangles.

Test points: the concept of similar triangles, the meaning of similarity ratios, and the enlargement and reduction of drawing figures.

Assessment requirements: (1) understand the concept of similarity; (2) Master the characteristics of similar graphics and the significance of similar ratios, and be able to enlarge and reduce known graphics according to requirements.

Test points: The theorem of proportionality of parallel lines and segments, and the theorem of parallel lines on one side of a triangle.

Assessment requirements: Understand and use the proportionality theorem of parallel lines and line segments to solve some geometric proofs and geometric calculations.

Note: The side that is judged to be parallel cannot be used proportionally as the corresponding line segment in the condition.

Test point: The concept of similar triangles.

Assessment requirements: Based on the concept of similar triangles, grasp the characteristics of similar triangles, and understand the definition of similar triangles.

Test Points: Determination and properties of similar triangles and their applications.

Assessment requirements: Proficient in the determination theorems (including the preparatory theorem, the three decision theorems, and the similar decision theorems of right triangles) and properties of similar three-confessional halls, and be able to apply them well.

Knowledge of functions and equations.

Error-prone point 1: The relevant concepts of rational numbers, irrational numbers and real numbers are misunderstood, and the meaning concepts of opposite numbers, reciprocal numbers and absolute values are confused. and the classification of absolute values and numbers. It is compulsory to choose every year.

Error-prone point 2: The key to mastering the concepts and properties related to real numbers and flexibly using various arithmetic laws is to control the symbols; In more complex operations, the order of operations is not paid attention to or the laws of operation are not used reasonably, resulting in errors in operations.

Error-prone point 3: the difference between square root, arithmetic square root, and cubic root. Fill-in-the-blank questions are mandatory.

Error 4: When the fraction value is zero, students tend to ignore that the denominator cannot be zero.

Error-prone point 5: Pay attention to the changes in the algorithm and symbols when operating fractional operations. When the numerator and denominator of the fraction is a polynomial, it should be factored first, and the factorization should be decomposed until it can no longer be decomposed.

Fill-in-the-blank questions are mandatory.

Error-prone point 6: The nature of non-negative numbers: the sum of several non-negative numbers is 0, and each formula is 0; overall substitution method; Completely flat.

The above is what is the key summary of the knowledge points of the junior high school mathematics common test that I have compiled for you.

Essential knowledge points of junior high school physics. 1. Light is an electromagnetic wave. Uses of light:

1) Light energy enables us to see objects (lighting), (2) Plants carry out photosynthesis, (3) Utilization of light energy (solar cars, solar water heaters, solar cells) (4) Optical fiber communication (5) Infrared remote control (6) Distance measurement using the speed of light (7) Laser guidance for tunnel engineering (8) Laser for medical treatment (9) Ultraviolet sterilization and disinfection, etc. 2. Light source: An object that can emit light is called a light source.

Natural light sources: the sun, fear of stars, fireflies, jellyfish, etc.

1. Light travels in a straight line in the same homogeneous medium. Light: A straight line with an arrow to indicate the direction and path of light.

Light is a man-made assumption that it does not exist) 2. The maximum propagation speed of light in a vacuum is meter seconds (m s), which is kilometers and seconds (km s) (the propagation speed in the air is slightly smaller, but it is also considered to be meter seconds (m s)). 3. Light-years: The distance that light travels in a year.

A light year is a unit of distance rather than a unit of time) 3. Reflection of light: 1. Definition: The phenomenon of light changing the direction of propagation at the interface between two substances and returning to the original substance.

2. The law of reflection of light: (1) When light is reflected, the reflected ray, the incident ray and the normal are in the same plane, (2) the reflected ray and the incident ray are located on both sides of the normal respectively; (3) Angle of incidence such as reflection angle. 3 The reflection of light is divided into specular reflection and reflection (they both follow the law of reflection of light) (the optical path is reversible in the reflection of light) Characteristics of plane mirror imaging:

1) The distance between the image and the object and the mirror is equal (equidistant); (2) The image is equal in size to the object (equal size). (3) the image and the object are symmetrical (symmetrical) with respect to the mirror; (4) The plane mirror is a virtual image. Fourth, the refraction of light

1.Definition: A phenomenon in which the direction of light travels as it moves from one substance to another.

2.The law of refraction of light: (1) When light is refracted, the refracted ray, the incident ray, and the normal are in the same plane; (2) The refracted rays and incident rays are located on both sides of the normal; (3) When the air of the light cluster obliquely enters the transparent material such as water and glass, the refracted ray is deflected to the normal, and the refractive angle is small and the incident angle is small; When transparent substances such as light plexus water and glass are obliquely emitted into the air, the refractive angle is greater than the incident angle. When the angle of incidence increases, the angle of refraction also increases, and the direction of propagation does not change when the light hits the surface of the medium perpendicularly.

The angle in the air should be larger) (the light path is also reversible in refraction) (the angle in the air during refraction> the angle in the water > the angle in the glass, 5. Convergence: convex lens, concave mirror. Divergence:

Concave lenses, convex mirrors.

The knowledge points of the third year of mathematics are as follows:1. An integer equation that contains two unknowns and the highest number of unknowns is 1 is called a binary one-time Qi sell-a program. 2. The circumferential angle of the same arc or equal arc is equal; In the same circle or equal circle, the arcs opposite the circumferential angles of the same circle are also equal.

3. The values of two unknowns that make the values of the two equations on the left and right sides of the binary linear equations equal are called the solutions of the binary linear equations.

4. If the coordinates of the two intersection points of the function image and the x-axis are known, they can be set to the intersection type.

5. The selection order of the solution method of the one-element quadratic equation is: special first and then general, if there is no requirement, there is generally no need to match the method.