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Adding/subtracting negative numbers

Adding and subtracting negative numbers

Adding/subtracting negative numbers

Discussion and questions for this video
what happens if you get 7+-4???? does the minus still turn into a +?
I still don't understand adding and subtracting negative numbers. I need some help could someone explain this to me or refer me to a site or book that will explain adding and subtracting negative numbers, please!
Now I understand how to add and subtract and it has helped me in school. But, how do you subtract when you have three numbers? ex: 18-(-17)-(-11)
18-(-17)-(-11) = 18+17+11 = (18+17)+11 = 35+11 = 46
if you have 18-17-11 then the answer will be like this:
18-17-11 = (18-17)-11 = 1-11 = -10
so when u hav a problem like 2--3 then u wood just change the minus into plus and the negative into positive? im trying to make things more simple for my brain!!! :)
Yes, basically! Copy, Change, Change. It was the method I was taught!
why dont u get the same answer when u subtract -3 - -3 as to when u subtract -3 - 3
because when you subtract a negative it is really like adding a positive so really your equation is -3+3 which equals 0
illustrate using the number line why subtracting a negative number from another
negative number that it is necessary to change the sign of the subtracting number
to a positive to get the correct answer or is it the case of a rule that must be
learned with no reasoning behind it. sal passed over this in the video.

Why do negative number's cancel out?
Because negative numbers are the opposite of positive numbers.
Why does Sal use a shorthand notation at 5:43?
what about an equation like 1+-9???now what do I do???
The above answer is incorrect.

Grace, remember that 1 + -9 is the same as -9 + 1. Think of it this way. When using a positive number you move to the RIGHT on a number line. When using negative numbers, you move to the LEFT on the number line.

Put your finger on -9. To add 1, you will move 1 space to the RIGHT. Now where is your finger? On -8 correct? That is your answer.

Likewise you could put your finger on 1. Then move your finger to the left 9 spaces. Now where is your finger? -8? See you got the same answer.

Good Luck
Sal makes it easier to understand..
but when you add a two negatives isn't it the same as adding two positives?
can you subtract a negative number the traditional way , and then just make the answer a negative number?

example: problem: 12-15 (so i would turn that into: ) 15-12= 3, and then I would turn 3, into -3

does that always work? (:
you too.... re-watch the video until you get it! :)
wats a nother way instead of using the number line
switching the signs or using paper or some other material chips and laying them out, and then canceling. look on other websites too for further help if your arent finding your answers here.... :)
When he says "3 minus minus 3'' does he mean 3 minus negative 3?
how would you subtract -8 from 1?
1-(-8)=9 not -9. Normally, you move left on the number line when you subtract. But when you subtract a negative number, you have to move the opposite way. Minus a negative is the same as adding.
Do you get a negative number if you subtract a negative number from a negative number?
this is so much harder than multiplying/dividing integers to me. why could that be.
Maybe because multipliying and dividing fractions is more easy then adding and subtracting them.
A little confusing about the negative - negative and how it almost makes a positive.
make a number line in your brain.then you will see
do you always have to write/draw a number line?
i dont get that if -50 is a smaller amount then -20then how do u minus -20 from - 50????
would it just be -30??? or is there somthing i am missing
-20 - -50 = 30 (remember that the double minus cancels itself out so it becomes a plus, like the video says).

However, -50 - -20 = -30 (again, the double minus cancels itself out and becomes a plus).

Make sense now?
im just confused about this
search further into the web....theres tons of info out there! :)
How whould I solve this -3 + 4 ( -2 ) or which video can I refer to ?
It might be easier to split the expression into smaller parts: 4 - 2 = 2 thus the expression becomes -3 + 2 Then we can replace those two numbers by their negations (their corresponding negative or positive numbers): 3 - 2 = 1 and then negate the whole expression: -1

Or you can just negate it from the very beginning:
-3 + 4 - 2 = -(3 - 4 + 2) = -(3 + 2 - 4) = -(5 - 4) = -1
Why do the signs in the problem 2--3 become addition or cancel such as in the video of adding/subtracting negative numbers at 5:27 on the timer?
Because the "-" sign negates (or changes the sign of) the expression: -1 is the negation of +1 and +2 is the negation of -2. The author of the video should have read "two minus negative three" instead of "two minus minus three". It makes more sense. So, you are negating the number -3 (negative three).
I still don't understand it.HELP!!!
@mvu347: I think that this is fine. People do that all the time when they need help and there is nothing wrong with it.
so, what you mean is,subbtracting negativie numbers turn in to adding,and adding negative numbers turn in to subtracting,right??
ok what about if I have -(-4)-(-8) = ?
i don't understand why -3++3=0...please can anyone answer please
to make it simpler think it as -3+3 so if u start at the negative side of the numberline at -3, then u encounter the plus sign so u move to the right 3 times so u reach 0
a negative plus a positive equals a negative right and a negative plus a negative equals a bigger negative right? b cause if its true i am such a genius!!!!!!!!!!!!!!
No. -3+6=3. But your second theory is correct.
I still dont get it so can someone please help me summarize this in detail the differences between getting a positive number and a negative number? Thank you.
well a positive number is above 0 & a negtive is below 0 (read slow)
I am still struggling, could anyone help me?
sorry this isnt an awnser but fear not i dont get it either!!!!!!! /:I
I just don't know all the rules!
E. -5+-7=?
I don't get it

"I am a student here help me'!!!!!!!'!!!!!!!!!!!!!!!!!!!!!!''!!!!!!!!!!!!!!!!"
Your frustrated pupil,
-5+-7 is the same as -7+-5. What happens if the problem was -5+7?

2 would be the correct answer, but the 7 is a negative. So what would 5+-7 be?

-2 would be the answer, because 5+-7 is the same as 5-7. so what does it mean to add a negative number? Adding a negative is the same as subtracting a positive. 5+-7 = 5-7. That means -5+-7 is the same as -5-7 or -7-5. Now you tell me,

What is -5+-7?
Hmmm....the following still bugs me....when you have somthing like:

8 - - 7 = ?

I understand the procedure...2 minus signs become plus sign and you add the numbers to get 15. Messes me up, though. Can someone explain this? I read it as if we're suppose to subtract a neg 7 from 8. A real world example would help, too. thanks, cheers.
When you see a minus and a minus, just change it into one plus. If you see a minus and a plus or a plus and a minus, change it into one minus. If you see a plus and a plus, change it into one plus. Thus 8 --7 is 8+7 = 15, and 8+-7 is 8-7 = 1, and 8-+7 is 8-7=1, and lastly 8++7 is just 8+7=15
I can't visualize 3 - -3 on the number line. Can't that be shown too? Just to say the minuses cancel out is not a full answer. How do they cancel out?
yes it can when you draw the # line it will go back 3 from 3 so its 0 on the # line quite simple really
None of this video helps me with this excersises, only the comments
videos help me a bit but comments help me a lot
i am still struggling boooooohoooooooohoooooohoooooohooo
i feel sorry for you



why does is have to be so confussing?!?
i dont think anything is confusing not trying to brag.... but like which ones are you confused on? like the ones where you have to have a positive number plus a negitive number?
all you have to do is make it all positive and the opisite operation such as 5+-7
just make the operation its opisite which is subtraction and make that negitive seven positive all you have to do now is answer the question and your answer would be a negitive number but that's just how it works so your answer would be -2 btw-(by the way) glad i could help :)
Report a mistake in the video

At 2:33, Sal said "single bonds" but meant "covalent bonds."

Report a mistake in the video

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