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Tìm các giá trị của x thỏa mãn hệ bất phương trình :
a. \(\left\{ {\begin{array}{*{20}{c}}{2{x^2} + 9x + 9 > 0}\\{5{x^2} – 7x – 3 \le 0}\end{array}} \right.\)
b. \(\left\{ {\begin{array}{*{20}{c}}{3{x^2} + 11x – 4 \le 0}\\{{x^2} – 8x – 20 \le 0}\end{array}} \right.\)
c. \(\left\{ {\begin{array}{*{20}{c}}{2\left( {x – 1} \right) – 3\left( {x – 4} \right) > x + 5}\\{\dfrac{{3x – 4}}{{{x^2} + 4x + 4}} \ge 0}\end{array}} \right.\)
d. \(\left\{ {\begin{array}{*{20}{c}}{\dfrac{{3{x^2} – 7x + 8}}{{{x^2} + 1}} > 1}\\{\dfrac{{3{x^2} – 7x + 8}}{{{x^2} + 1}} \le 2.}\end{array}} \right.\)
:
a. \(x \in \left[ {\dfrac{{7 – \sqrt {109} }}{{10}};\dfrac{{7 + \sqrt {109} }}{{10}}} \right];\)
b. \(x \in \left[ { – 2;\dfrac{1}{3}} \right]\)
c. \(x \in \left[ {\dfrac{4}{3};\dfrac{5}{2}} \right)\)
d. \(x \in \left[ {1;6} \right]\)