Generally speaking, chapters 1, 2 and 5 are the key points. 1, the operation of algebraic expression. In all the final exam papers, the first multiple-choice question must be the operation of algebraic expressions, which involves multiplication of products, multiplication and division of the same base, addition and subtraction of algebraic expressions. 2. Parallel lines and intersecting lines. You should know here: if the sum of two angles is a right angle, then these two angles are called complementary angles; If the sum of two angles is a right angle, then these two angles are called complementary angles; The vertex angles are equal; The same angle is equal; The same angle and complementary angle are equal; Equivalent substitution; The basis for judging the parallelism of two straight lines; Characteristics of parallel lines. 3. Scientific counting method of micron and nanometer, approximate to significant number (required) 4. Probability 5. Congruent triangles's certificate. The relationship between variable values: dependent variable, independent variable, algebraic evaluation, that is, bring the known number equal to X\Y\Z into the formula, first calculate the number in brackets, and then calculate the number according to. ! ! ~~~~~~~