4x²+20x+16<0.........

4x² + 20x + 16 < 0
----------------------------- : 4
x² + 5x + 4 < 0
(x+4)(x+1) < 0 (-)
x = -4
x = -1

substitusi nilai x = 0, maka didapatkan hasil (+)
maka
HP = { -4 < x < -1 }

4x² + 20x + 16 < 0
⇒ x² + 5x + 4 < 0
⇒ (x + 1)(x + 4) < 0
⇒ x = -1 atau x = -4
Garis Bilangan :
====-4======-1=====
Intervalnya :
++++ (-4) - - - (-1) ++++
Karena diminta < 0 maka :
HP = {x | -4 < x < -1}