Réponse :
Explications étape par étape
Bonjour
Dresser le tableau des signes :
1) A(x) = (1-2x) (x+2)
1 - 2x = 0 ou x + 2 = 0
2x = 1 ou x = -2
x = 1/2 ou x = -2
x........|-inf.........(-2)........1/2.......+inf
1-2x...|......(+)............(+)...o...(-)........
x+2....|......(-)......o....(+)........(+).......
EQU..|......(-)......o....(+)....o....(-).......
2)B(x) = 5x (3x-2) (x+5)
5x = 0 ou 3x - 2 = 0 ou x + 5 = 0
x = 0 ou 3x = 2 ou x = -5
x = 0 ou x = 2/3 ou x = -5
x.........|-inf.......(-5)........0.......2/3......+inf
5x.......|......(-)...........(-)..o.(+)........(+)........
3x-2...|......(-)..........(-).......(-).....o...(+).......
x+5.....|......(-).....o..(+).......(+).........(+).......
EQU...|......(-).....o...(+).o...(-)....o...(+)........
3)C(x) : (4-x)/(x + 3)
Avec x + 3 # 0
x # -3
4 - x = 0
x = 4
x........|-inf.........(-3)..........4.........+inf
4-x....|.......(+)............(+)...o...(-).........
x+3....|......(-)......o.....(+).........(+).......
EQU.|.......(-)......o.....(+)..o...(-).........
