pre- algebra help... negative or posative?

[lillybeth]

I have a question on my math homework and was wondering if someone could help me.

If m= -4 and n=7, what is the value of m-n? I don't know if the answer is -11 or 11 because:

There is more than one subtraction sign, so wouldn't that make it posative?

-4 - 7 = -11, right?

Please help!!!

Thanks!

 

[MarkFL]

...
-4 - 7 = -11, right?

Yes, that's correct.

(-4) - (7) = -4 - 7 = -(4 + 7) = -11

A rule I was taught with addition/subtraction, is that if the signs are the same then add the magnitudes (the numbers without the signs), then attach the sign that both originally have. Examples:

3 + 6 = +(3 + 6) = 9

-6 - 12 = -(6 + 12) = -18

If the signs are different, then subtract the smaller magnitude from the larger, then attach the sign that the number of greater magnitude originally had. Examples:

3 - 6 = -(6 - 3) = -3

-4 + 8 = +(8 - 4) = 4

 

[lillybeth]

Yes, that's correct.

(-4) - (7) = -4 - 7 = -(4 + 7) = -11

A rule I was taught with addition/subtraction, is that if the signs are the same then add the magnitudes (the numbers without the signs), then attach the sign that both originally have. Examples:

3 + 6 = +(3 + 6) = 9

-6 - 12 = -(6 + 12) = -18

If the signs are different, then subtract the smaller magnitude from the larger, then attach the sign that the number of greater magnitude originally had. Examples:

3 - 6 = -(6 - 3) = -3

-4 + 8 = +(8 - 4) = 4

OK. Thanks Bunches Mark! I guess the two subtraction thing is for multiplication. Thanks!

 

[MarkFL]

Yes, the product of two non-zero numbers of the same sign is always positive, and if the signs are different then the product is negative.

 

[lillybeth]

Yes, the product of two non-zero numbers of the same sign is always positive, and if the signs are different then the product is negative.

That's what I figured. Thanks!

 

[Deleted member 4993]

OK. Thanks Bunches Mark! I guess the two subtraction thing is for multiplication. Thanks!

The same rule applies for division (rule that you follow for multiplication).

Do be careful about subtraction of negative numbers. For example:

6 - (-7) = 6 + 7 = 13

-9 - (-6) = -9 + 6 = -3

 

[lillybeth]

The same rule applies for division (rule that you follow for multiplication).

Do be careful about subtraction of negative numbers. For example:

6 - (-7) = 6 + 7 = 13

-9 - (-6) = -9 + 6 = -3

Thanks!