Bonjour
1-. (1-4x)(x+1)>0
1 - 4x = 0 et x + 1 = 0
4x = 1 et x = -1
x = 1/4 et x = -1
x..........|-inf......-1.......1/4........+inf
1 - 4x..|......(+).......(+)..o...(-).........
x + 1....|......(-)...o..(+)........(+).......
Ineq....|......(-)...o..(+)..o...(-).......
[tex]x\in ]-1 ; 1/4[[/tex]
2-. x au carré ≥16
x^2 - 16 >> 0
x^2 - 4^2 >> 0
(x - 4)(x + 4) >> 0
x - 4 = 0 ou x + 4 = 0
x = 4 ou x = -4
x............|-inf........(-4).........4.........+inf
x - 4......|......(-)............(-)....o....(+)........
x + 4.....|......(-)......o....(+)..........(+)........
Ineq......|......(+)......o....(-)....o.....(+).......
[tex]x \in ]-\infty ; -4] U [4 ; +\infty[[/tex]
