Why is two negative sometimes positive sometimes negative?

Question

Its no wonder Im getting algebra wrong. My algebra book says

Negative and a negative is a positive

A postive and a positive is a positive

A negative and apositive is a negative.

Thats it Thats all.

BUT i have gone on here and some people say different.

They go on about 2 negatives being a negative NOT a positive.

And there right.

How do you know which rule to apply to what? I thought I had it now Im more confused than ever! :(

Answer 1

you can apply that in multiplication and division integers

Answer 2

I don't follow your question.

Answer 3

Those people are absolutely wrong IF YOU ARE TALKING ABOUT MULTIPLICATION, don't forget these questions are often answered by people who aren't as smart as you.

Two positives multiplied together are ALWAYS positive => 5 * 6 = 30

Two negatives multiplied together are ALWAYS positive => -2 * -7 = 14

A negative and a positive multiplied together are ALWAYS negative => 4 * -3 = -12

For ADDITION OR SUBTRACTION ONLY, you could end up positive or negative.  Think of this as you are standing on zero on a numberline, any negative numbers make you walk that far in the negative direction, any positive numbers make you walk in the positive direction.  Which ever is bigger will determine the sign.  So -10 +3, you walk to minus 10 on the number line, then walk back 3 in the positive direction, but that's not enough to get you back to zero, so you end up at -7.  If the positive number were bigger, such as -2 + 6, you end up on the positive side of zero, 4 in this case.

Answer 4

This should be easy let's see a

-2 + - 2=-4

-2 - 2=0

-2 - -2=4

rule of thumb in this instance is

a negative plus a negative will equal a negative

a negative minus a negative will egual a positive

all right let's go over it with different numbers

-7 + -10= -17

-7 - 10 = 3

-7 - -10= 17

simple algebra

Answer 5

chill

plzzz answer

http://answers.yahoo.com/question/index;...

Answer 6

Ok here's the deal:

when using multiplication or division,

if the signs are the same, the answer will be positive

if the signs are different, the answer will be negative

In other words, your algebra book is correct.

Answer 7

When multiplying two numbers, two positives make a positive as do two negatives. A negative times a positive equals a negative number regardless of which of the two is positive and which is negative.

When adding two negatives, a negative will always result. When adding two positives, a positive will always result. When adding a positive and a negative, the result could be positive or negative depending on the sizes of the two numbers.

{added]

Okay. Well then what about subtraction and addition?

Heres an explanation

-5 + -3 = - 8

Rules dont work there...

Actually, they do. Adding two negative numbers results in a larger negative number than either of the two numbers being added. Since 5 + 3 = 8, -5 + -3 = -8.

Think of it on the number line:

From a position 5 units to the left of 0, add in an additional 3 units further left. The final position is 8 units left of 0 or -8.