Guide 4, Problem Set on page 135, Number 10

[cosmichay]

Hi,

I need help with the problem number 10. In the Solutions explanation, it says that q must be negative and r must be positive. Why? It wasn't said so in the questions and I'm not aware of any rule that implies so. Can somebody please explain this?

Thanks.

[tommywallach]

Hey Cosmic,

If r = -2q, that tells you that r and q have different signs (one is positive, one is negative). We also know from the picture that r is bigger than q (because it's to the right on the number line). That means that r is positive and q is negative. Make sense?

-t