Junior one mathematics mainly studies rational numbers, addition and subtraction of algebraic expressions, linear equations with one variable, geometric figures, intersecting lines and parallel lines, real numbers, linear equations with two variables and other important knowledge points.

Junior high school mathematics volume I Junior high school mathematics volume II Junior high school mathematics important content (1) One-dimensional linear equation

Equation (1): first, let letters represent unknowns, and then write an equation containing unknowns according to the equation relationship, which is called an equation.

(2) One-dimensional linear equation

One-dimensional linear equation refers to an equation with only one unknown number, the highest order of which is 1, and both sides are algebraic expressions, which is called one-dimensional linear equation. Finding the value of the unknown quantity in the equation is called the solution of the equation.

(3) Properties of the equation

① Adding (or subtracting) the same algebraic expression on both sides of the equation is still valid.

If a=b

Then a+c=b+c

② Both sides of the equation are multiplied or divided by the same non-zero algebraic expression at the same time, and the equation still holds.

If a=b

Then there is a c = b c or a \c = b \c(c≠0).

③ The equation is transitive.

If a 1 = a2, a2 = a3, a3 = a4, ... an = an, then a 1 = a2 = a3 = a4 =...= an.

(3) Steps to solve the equation

The steps to solve a linear equation with one variable are: removing denominator, brackets, shift terms, merging similar terms, and converting unknown coefficients into 1.

(1) Denominator: Turn the coefficient into an integer.

(2) brackets.

③ Shift term: shift the sign of an item on one side of the equation to the other side.

(4) Merge similar items.

⑤ The coefficient is 1.

Unequal and unequal groups

(1) inequality

Using inequality symbols (

(2) the essence of inequality

① symmetry;

② Transitivity;

③ monotonicity of addition, that is, additivity of inequality in the same direction;

④ Monotonicity of multiplication;

⑤ Multiplicity of positive inequality in the same direction;

⑥ Positive inequalities can be multiplied;

⑦ Positive inequalities can be squared;

(3) One-dimensional linear inequality

A formula connected by an inequality symbol contains an unknown number whose degree is 1, whose coefficient is not 0, and whose left and right sides are algebraic expressions is called one-dimensional linear inequality.

(4) One-dimensional linear inequalities

The group of one-dimensional linear inequalities consists of several one-dimensional linear inequalities with the same unknowns.