1, binary linear equation: An equation with two unknowns and the degree of the unknowns is 1 is called binary linear equation. 2. A formula that is connected by an inequality symbol and contains an unknown number, the degree of which is 1, the coefficient of which is not 0, and the left and right sides are algebraic expressions is called one-dimensional linear inequality.

3. Translation means that all points on the map move the same distance along a straight line in the same plane. This kind of graphic movement is called graphic translation movement, which is called translation for short.

4. In the same plane, there are two positional relationships between two straight lines: intersecting and parallel. If two straight lines have only one common point, they are said to intersect.

5. The square root is also called quadratic square root, which means √ ~ The square root that belongs to non-negative number is called arithmetic square root. Positive numbers have two real square roots in opposite directions, while negative numbers have no square roots.