GMAT Math

BlindVision wrote:It's been aeons since I've taken Algebra and wanted to kindly ask for help on refreshing the alegabraic sign operations...

1) -1(-8) = +8 ?

2) -(-8) = +8 ?

3) Can -y +8 be rewritten to y - 8 ?

4) Can -y - 8 be rewritten to y + 8 ?

I know it sounds silly of me to ask these questions but I really don't want to get any fundamental operations wrong on the real thing! Thank you for not laughing :D

A great way to learn is to ask - no one will laugh here!

Both 1) and 2) above are perfectly correct. When you multiply two negatives together, you will always get a positive.

In 3) and 4), however, when you reverse every sign, you are actually finding the negative of the expression you start with - you've multiplied each expression by -1. You can see this easily enough by choosing a number for y. Look at 3), and plug in y = 4. Then -y + 8 = -4 + 8 = 4. On the other hand, y - 8 = 4 - 8 = -4. The same will happen with the expression in 4) if you plug in any number you like for y.