x²- 5x +4 >0
Δ= 25 - 16 =9
x₁ = 1
x₂= 4
x I -∞ 1 4 ∞
------------I--------------------------------------------------------------------------------------------------
ex. I + + + + 0 - - - - - - - - - 0 + + ++ ++ + ++ + + + +
ex >0 daca x∈ ( -∞ , 1] U [ 4 , ∞)