Réponse :
Bonjour,
[tex]3(4x + 1) = -5(4 - 2x)\\\\\Leftrightarrow 12x + 3 = -20 + 10x\\\\\Leftrightarrow 12x - 10x = -20 - 3\\\\\Leftrightarrow 2x = -23\\\\\Leftrightarrow x = -\dfrac{23}{2}[/tex]
[tex]Donc \ S = \left \{-\dfrac{23}{2} \right \}[/tex]
[tex](9x + 3)(20 - 4x) = 0\\\\[/tex]
[tex]Or \ A \times B = 0 \Leftrightarrow A = 0 \ ou \ B = 0[/tex]
[tex]9x + 3 = 0\\\\\Leftrightarrow 9x = -3\\\\\Leftrightarrow x = -\dfrac{3}{9}\\\\\Leftrightarrow x = -\dfrac{1}{3}\\\\ou \\\\ 20 - 4x = 0\\\\\Leftrightarrow -4x = -20\\\\\Leftrightarrow x = \dfrac{-20}{-4}\\\\\Leftrightarrow x = 5[/tex]
[tex]Donc \ S = \left \{-\dfrac{1}{3} \ ; \ 5 \right \}[/tex]
