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解一元一次不等式组时,应首先求出这个不等式组中每个不等式的解集,然后利用数轴求出这些不等式解集的公共部分,即求出了这个一元一次不等式组的解集.“同大取大,同小取小,大小交叉中间找,大小分离无处找(空集)”,这四句话概括了求一元一次不等式组解集的四种情况.例1 解不等式组 3(1－x)< 2(x＋9),1 ＋1≥5－,2 2x－7≤4x＋7.3 解：由1得：x >－3.由2得：x ≥.由3得：x ≥－7.∴该不等式组的解集为：x ≥.当不等式组里几个不等式的解集都是大于号时,该不等式组的解集取其中最大的数,即“同大取大”. ＋1>x＋, 1
When solving a unitary inequality group, we should first find the solution set of each inequality in the inequality group, and then use the number axis to find the common part of the solution set of these inequalities. That is, we obtain the solution set of this unary inequalities group. Large, large, small, small, middle size, crossover, size separation, nowhere to find (empty set). These four sentences summarize the four cases of solving a set of inequalities for a single inequality. Example 1 Solution inequality group 3 ( 1-x)< 2(x+9),1 +1≥5-,2 2x-7≤4x+7.3 Solution: From 1: x >-3. From 2: x ≥. From 3: x ≥-7 ∴ The solution set of this inequality group is: x ≥. When the solution sets of several inequalities in the inequality group are all greater than the number, the solution set of the inequality group is taken to be the largest of these, ie, “majority to large”. +1 >x+, 1