Đáp án: $x\in\{-4,-3,-2,-1,0,1,2,3,4,5,6\}$
Giải thích các bước giải:
Ta có:
$\dfrac{5}{17}+\dfrac{-4}{19}+\dfrac{-20}{21}+\dfrac{12}{17}+\dfrac{-11}{31}<\dfrac{x}{9}\le \dfrac{-3}{7}+\dfrac7{15}+\dfrac{4}{-7}+\dfrac8{15}+\dfrac23$
$\to (\dfrac{5}{17}+\dfrac{12}{17})+\dfrac{-4}{19}+\dfrac{-20}{21}+\dfrac{-11}{31}<\dfrac{x}{9}\le (\dfrac{-3}{7}+\dfrac4{-7})+(\dfrac7{15}+\dfrac8{15})+\dfrac23$
$\to 1+\dfrac{-4}{19}+\dfrac{-20}{21}+\dfrac{-11}{31}<\dfrac{x}{9}\le (\dfrac{-3}{7}-\dfrac4{7})+1+\dfrac23$
$\to \dfrac{12369}{12369}-\dfrac{2604}{12369}-\dfrac{11780}{12369}-\dfrac{4389}{12369}<\dfrac{x}{9}\le -1+1+\dfrac23$
$\to -\dfrac{6404}{12369}<\dfrac{x}{9}\le \dfrac23$
$\to -\dfrac{19212}{4123}<x\le \:6$
$\to -4\le x\le 6$ vì $x\in Z$
$\to x\in\{-4,-3,-2,-1,0,1,2,3,4,5,6\}$
