Bonsoir
4x(2x + 7) << 0
4x = 0 et 2x + 7 = 0
x = 0 et 2x = -7
x = 0 et x = -7/2
x............|-inf..........-7/2........0.........+inf
4x.........|........(-)..............(-)...o....(+)........
2x + 7...|........(-)......o.....(+)........(+)........
Ineq......|........(+).....o.....(-)...o....(+).......
[tex]x \in [-7/2 ; 0][/tex]
-x(-4x + 1)(x + 6) < 0
-x = 0 et -4x + 1 = 0 et x + 6 = 0
x = 0 et 4x = 1 et x = -6
x = 0 et x = 1/4 et x = -6
x............|-inf.......-6........0.........1/4.........+inf
-x...........|......(+).......(+)...o...(-).........(-)...........
-4x + 1...|......(+).......(+)........(+)...o...(-)..........
x + 6.....|.......(-)...o...(+)........(+).........(+)........
Ineq......|.......(-)...o....(+)..o...(-)..o.....(+)........
[tex]x \in ]-\infty ; -6[ U ]0 ; 1/4[[/tex]
