Test center: Linear function can obtain information through function images, develop visual thinking, understand two conditions to determine a linear function, solve some simple linear function expressions from two conditions, skillfully make images of linear functions, understand the relationship between equations and images, and clarify the expressions of linear functions and proportional functions. Difficulties: real numbers, knowing the concepts of arithmetic square roots and square roots of numbers, will use the root sign to represent the arithmetic square roots and square roots of a number, and understand that square roots and square roots are reciprocal. We will use this reciprocal operation relationship to find some non-negative arithmetic square roots and square roots, and pay attention to the differences and connections between square roots and arithmetic square roots. The difference is that positive numbers have two square roots, while arithmetic square roots have only one. The connection is that the positive square root of a positive number is its arithmetic square root and the negative square root is the opposite of its arithmetic square root. So you can write its square root immediately according to its arithmetic square root, find the square root and cube root with a calculator, and understand the meaning of real numbers. Emphasis: the exploration of binary linear equations and quadrilateral properties. Binary linear equations: Understand binary linear equations, and judge whether a set of numbers is a solution of binary linear equations, solve binary linear equations by substitution elimination method and addition and subtraction elimination method, list the corresponding binary linear equations according to the meaning of the question, and solve and understand the relationship between binary linear equations and functions. A probe into quadrilateral properties: 1. Using the properties of parallelogram, we can find out the degree of angle and the length of line segment, and also prove that angle, line segment and bisector of line segment are equal. 2. Explore and master the discriminant conditions of parallelogram. To judge whether a quadrilateral is a rhombus, it is generally judged that the quadrilateral is a parallelogram first, and then a group of adjacent sides are equal or diagonal lines are perpendicular to each other. 3. Trapezoids and rectangles are also judged by definition. 4. After that, the sum of the inner and outer angles of the polygon will be judged. 4. You can draw a figure with a symmetrical center, which can be rotated or translated. That's all I can summarize. Others need your efforts! ! !