不等式的常见性质有三条.性质1:不等式两边加(或减)同一个数(或式子),不等号的方向不变.即,若a>b,则a±c>b±c.性质2:不等式两边乘(或除以)同一个正数,不等号的方向不变.即,若a>b,c>0,那么ac>bc(或a/c-b/c).性质3:不等式两边乘(或除以)同一个负数,不等号的方向改变.即, There are three common properties of inequalities. Property 1: Inequalities add (or subtract) the same number (or formula) on both sides, the direction of the inequality is constant. That is, if a>b, then a±c>b±c. : Inequalities multiply (or divide by) the same positive number, the direction of the inequality sign is unchanged. That is, if a>b,c>0, then ac>bc (or a/cb/c). Property 3: Inequalities on both sides (or divide by) the same negative number, the direction of the inequality sign changes. That is,