The operation of rational numbers in junior high school is divided into addition, subtraction, multiplication and division, and addition is divided into addition with the same sign and addition with different sign. The addition operation has some exchange laws and associative laws.
The multiplication rule of rational numbers is: two numbers are multiplied, the same sign is positive, the different sign is negative, and the absolute value is multiplied. The corresponding multiplication exchange law, association law and distribution law.
Intersecting line and parallel line
① Understand the complementary angle, complementary angle and antipodal angle, and know that the complementary angle, complementary angle and antipodal angle are equal.
Understand the concepts of vertical line and vertical line segment, the shortest nature of vertical line segment, and the significance of the distance from point to line.
(3) if you know that there is a point and only one straight line is perpendicular to the known straight line, draw a straight line perpendicular to the point with a triangular ruler or protractor.
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Quadratic roots are difficult for many students to simplify because of their changeable forms and flexible methods, but this part of knowledge should not be abandoned in junior high school mathematics content.
The basic expression of quadratic function is y=ax? +bx+c(a？ 0)。 The highest order of a quadratic function must be quadratic, and the image of a quadratic function is a parabola whose symmetry axis is parallel or coincident with the Y axis.
The expression of quadratic function is y=ax? +bx+c (and a? 0), defined as quadratic polynomial (or monomial).
If the value of y is equal to zero, a quadratic equation can be obtained. The solution of this equation is called the root of the equation or the zero of the function.
? Preliminary probability?
(1) Discrimination of inevitable events, impossible events and random events;
(2) Cognition of the definition of probability (classical probability);
(3) use? List method? Or? Tree diagram? List all possible results, and then calculate the probability;
(4) What happened to an event in the experiment? Frequency? Estimate the probability of this event.