anonymous 5 years ago with quadratic equations how do I know when to add or subtract!

1. anonymous

2. anonymous

well with $1\pm \sqrt{1^2 -4(1)(-4)}$ would this be a situation to add since a neg 4 times a neg 4 is a positive 16

3. anonymous

4. anonymous

okay beacuse in my math book there is a similar one and they subtracted. it was $-2 \pm \sqrt{2^2 - 4(5)(-2)} \over 2(5)$

5. anonymous

Well, you add inside the square root for both cases because you're multiplying two negative numbers together.

6. anonymous

right but the answer in the book depends on it being subtracted. So is the book just plain wrong?