Name: Sean

Who is asking: Student

Level: Elementary

Question:

I have a question about an inequality problem. Here it is: Solve and graph 5 - 3x => 17. (=> is greater than or equal). Please tell me why you flip the inequality sign when divinding by a negative number.

Thanks.

Sean

Hi Sean,
It has to do with the way we order the numbers. 20 is greater than 5, but -20 is less than -5. (20 degrees is warmer than 5 degrees but -20 degrees is colder than -5 degrees.) Using the inequality symbol

20 > 5 but -20 < -5
In the inequality above, when you multiply "20 > 5" on both sides by -1 (or divide by -1), the inequality changes direction.
I hope this helps,

Penny