So sánh a và b, biết

K

khaiproqn81

−23a−34≥−23b−12⇔−23a+23b≥34−12⇔−23(b−a)≥14⇔23(a−b)≥14⇔a−b≥38⇔a>b\dfrac{-2}{3}a-\dfrac{3}{4} \ge \dfrac{-2}{3}b-\dfrac{1}{2} \\ \Leftrightarrow \dfrac{-2}{3}a+\dfrac{2}{3}b \ge \dfrac{3}{4}-\dfrac{1}{2} \\ \Leftrightarrow \dfrac{-2}{3}(b-a) \ge \dfrac{1}{4} \\ \Leftrightarrow \dfrac{2}{3}(a-b) \ge \dfrac{1}{4} \\ \Leftrightarrow a-b \ge \dfrac{3}{8} \\ \Leftrightarrow a>b
 
K

khaiproqn81

12a−53≤12b−4⇔12(a−b)≤−73⇔a−b≤−143⇔a<b\dfrac{1}{2}a-\dfrac{5}{3} \le \dfrac{1}{2}b-4 \\ \Leftrightarrow \dfrac{1}{2}(a-b) \le \dfrac{-7}{3} \\ \Leftrightarrow a-b \le \dfrac{-14}{3} \\ \Leftrightarrow a<b
 
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