I'm going to show you how to subtract integers using a number line. Not too many textbooks
actually demonstrate this process. But it's kind of cool, weird, but cool. and many
students do like to use this. So it's
worth showing. Alright, it's there's adding and subtracting on here. So,
you have to take into consideration the
operation (adding or subtracting) and then what
you are adding or subtracting the second
number. So in this particular first
problem, we've got
2+3. So we're going to start at the 2 and
then we're going to face in the positive
directions. So you face , right here all
these directions, faced the direction of
your operation, and then we're going to
move in that direction.
3. So, 1, 2, 3. And we end up with 5. That one works. Alright 5-3, alright, in this case we're going to start at the
5, and the operation is subtraction, so we are going to face a negative direction and move
forward
3. 1, 2, 3. We end up with 2. That's another one you probably knew.  Here the signs are
different.  We're going to start with a subtraction and we're going to add a positive. So we start with negative 2 and face we're going to face
positive and we're gonna walk in the
positive direction so we've got positive,
positive. So it's going to go 1, 2, 3, 4. And we end up with a 2. So negative 2 plus 4 is a 2. I'm going to show you another way
when we do the practicing. But, right now I'm just using the number line. Here we're going to start at
negative 2. And we're going to face in
the negative direction. And we're going
to walk a positive 4. 1, 2, 3, 4. And we end up with negative 6. So,
negative 2 minus 4 is negative 6.
Now on this next page it gets more complex because
the second number is negative in each
case. And we are actually going to be moving backwards. So I'm going to start at  3. And we're adding, so the operations
positive, we're going to go positive face the right
direction, but we're going to walk backwards. 1, 2, 3, 4. And we end up with negative 1. So, 3 plus
a negative 4 is negative 1. We actually knew this from when we were adding signed numbers. Here we're subtracting  a negative. Alright, I'm going to start at 3. This is a tricky one. Start at 3. Face left
because the operation is subtraction. But we're are going to walk backwards.  1, 2, 3. And we end up at 6. So 3 minus a negative 3 (we call that snake eyes) is a 6. Here we're going to start at
negative 2. We're adding, so we are going to go forward or towards the
right but we're gonna walk backwards
because it's negative 1. We're going to end up at negative 3. So negative 2 plus a negative
1 is a negative 3. We learned that in the last video from money. But, here we're subtracting
a negative. This is probably the most
complex one. We start at negative 2. We face
negative because we're subtracting. But we're going to walk backwards because it's a negative
1. So negative 2 minus a negative 1 is negative 1.
In the next video I will show you how to do these without a number line, much more quickly.
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