Algebra Guide 4th Edition--noob question

[math noob]

Hi,

I haven't done math in years and have forgotten many of the basics, even to the point where the guides are too advanced in some respects. Anyways, concerning the 'select one or more' practice question on page 26, what part of the statement indicates that [a] x [b] must be positive? Do the straight-line brackets preclude negative values?

Thank you

[hhussain85]

This questions pertains to the associative property of multiplication which states the order in which multiplication occurs is irrelevant in a problem involving only multiplication.

In other words, -(a*b) = -a*b. The parentheses make no difference.

(-1)(a)(b) = (-1*a)*b = -1(a*b) = -1*a*b

I hope this helps.

BTW, I also had this problem until I brushed up on my mathematics.

[tommywallach]

Hey Math,

Yes, these are called absolute value symbols. They do indeed preclude negative values (best way to think of it as distance from zero, so [-8] = 8, because -8 is eight units away from zero). If you're taking our class, we go through all this in session 2. If you're not...you'll need to go find a basic math primer before you start our books. We sell a book called "Foundations of Math" for the GMAT, and pretty much everything in there pertains to the GRE. You could start there, or find some other similar book.

Good luck!

-t