Thursday

January 19, 2017
Posted by **Labz** on Monday, June 4, 2012 at 9:19pm.

(5x + 4)(x - 4) < 0

- Math -
**Reiny**, Monday, June 4, 2012 at 10:13pmHere is how I do these type of questions:

Critical values are x = -4/5 and x = 4

Mark these on a number line, splitting the number line into 3 distinct parts

< -4/5

between -4/5 and 4

> 4

Pick any value in each of the regions, if that value satisfies the original inequation, so will every other value in that region

You don't have to actually evaluate, just consider the sign

1. let x = -10

(-)(-) --> + , no good

2. let x = 0

(+)(-) --> , that works

3. let x = 10

(+)(+) --> + , no good

so -4/3 < x < 4