Up next in 10
We're continuing our series with integers and in our last session, we talked about how to add integers. We'll now move on to section 2 and discuss subtracting positive and negative integers. This can be very challenging for some students but we'll try to make it palpable.
Chapters:
00:00 Introduction
00:39 Subtracting Integers using the number line
01:55 Real life example
02:30 How To subtract positive integers
04:03 Real life example
04:23 How To subtract negative integers
06:50 practice problems
Show More Show Less View Video Transcript
0:00
okay so we talking about subtracting
0:02
integers right subtracting
0:05
integers so we just talked about adding
0:07
them and now we're going to talk about
0:09
subtracting the thing is
0:12
this like I said in the last section
0:16
these are key to everything that we
0:19
going to do from here which is equations
0:22
inequalities fractions we're going to
0:25
talk about all of this so we we have to
0:26
like really pay attention and get this
0:28
right so if you don't understand is you
0:30
need to spend time on the weekend
0:32
studying that so now first we're going
0:36
to talk about what it looks like on the
0:39
number line how does I show on the
0:41
number line how do you subtract integers
0:42
using the number line right so if you
0:45
look at my number line here I am trying
0:47
to do 4 - 9 all right that's what I'm
0:51
trying to do 4 - 9 and I need you all to
0:55
take notes because if you don't
0:56
understand it you better take notes or
0:58
you may have to go back and watch watch
1:00
this I'll go back and watch it okay so
1:02
it's up to you so we doing four - 9 so
1:05
if that four is on the right side of
1:08
zero right CU I have 1 2 3 4 I'm here
1:12
right and I want to take away from four
1:15
nine so if I'm
1:17
here and I want to take away 9 from four
1:20
I'm going to
1:21
go 1 2 3 4 5 6 7 8 and nine right four
1:28
from nine and now I land over here I
1:31
land at where -5 because I'm on the left
1:34
side of zero right so 4 - 9 is
1:37
technically saying 4 + -9 which is what
1:43
55 so 4 - 9 is five now the way I
1:47
thought this like for the last couple of
1:50
years is this assume that you have $4 in
1:53
your
1:55
account right assume that you have $4 in
1:58
your account and and then you spend
2:02
$9 now what happens you have negative
2:06
you have negative you owe money you owe
2:10
$5 right so you owe five and when you
2:13
owe is it positive or negative negative
2:15
negative so therefore 4 - 9
2:19
is5 right so you have to be careful with
2:22
that because as we go on it's going to
2:24
get harder right so now we're going to
2:26
learn so the first thing is this we're
2:28
going to learn how to subtract
2:30
positive integers right we're going to
2:35
learn how to subtract positive integers
2:38
okay so I have
2:42
-7 and I'm taking it away from -7 3
2:46
right so -7 is on this side of um zero
2:49
on the left side of zero and I want to
2:52
take away from this three so am I going
2:54
to go right or left left so if I'm here
2:57
I'm going to go 1 2 3 Aline where
3:00
10 -10 so -3 - 7 is -10 this is proba
3:06
probably by far the most confusing out
3:08
of every single one of them a lot of
3:10
people get confused with this right
3:13
because 7 - 3 can also be written as
3:16
what -7 + -3 so if you one of those that
3:21
don't get it if you ever see something
3:23
like this like -2 - 3 just go ahead and
3:26
change it so that we make sense to you
3:28
it's basically saying
3:31
-2 + -3 and that gives you5
3:36
or that's a negative times a negative is
3:40
a positive right but a negative plus a
3:43
negative gives you a negative because
3:46
you suppose you owe seven and then you
3:49
spend another three you're still
3:52
what negative you still in De you still
3:55
have a negative right so a negative plus
3:57
a negative is a negative okay so if you
4:01
owe
4:02
$7 and you spend another $3 now what do
4:05
you have you owe $10 you're still short
4:09
okay so the key is this if you have this
4:13
a succession of negative like that so
4:15
just use the plus sign so it helps you
4:18
okay now the next one is subtracting a
4:22
negative integer now this one is the
4:25
funnest this is this one I like the most
4:27
right because if I have negative 7 - -3
4:31
guess what I do it make it a positive
4:33
I'll make it a positive you see this
4:35
right you see this here you make it a
4:38
positive you have two negatives you
4:40
automatically make it a positive okay 7
4:43
- -3 is 7 + 3 so change it so this is
4:47
what we did last year we I learned from
4:49
Reagan she used to love doing this she
4:50
used to put it like this and turn into a
4:53
positive so that becomes 7 + 3 that
4:55
becomes 10 she love doing it right which
4:59
s
5:01
oh right and then here we have -7 minus
5:05
-3 right same thing yeah if the so if
5:09
the I not so if the negatives are are
5:12
next each other that equals a positive
5:14
that equals a positive so right if the
5:17
negative are next to each other it
5:18
becomes a positive same thing here I
5:20
have -7 - -3 becomes 7 + 3 and that
5:25
equals what4 because you
5:28
ow7 7 and you add $3 add three you still
5:33
owe $4 still owe right and that's a
5:36
negative so now what we're going to do
5:37
is I going to have you guys work on
5:39
several examples to see if you
5:42
understand it okay because we have to do
5:44
that the only way to understand
5:46
something is to work on more
5:48
problems this is how you learn okay so
5:52
let's go ahead and do this here let me
5:54
actually can I eras this yeah right
6:02
so examples we're going to work on some
6:04
examples so let's say we have
6:07
10 -
6:09
[Music]
6:11
19 10 + -19 and then we have uh
6:19
7 -
6:22
20 and then
6:25
-7
6:27
- 10
6:31
[Music]
6:40
and
6:43
12 what
6:49
color all right let's do this what color
6:53
pink all
6:55
right so what do you all think -10 - 19
6:58
is going to be
7:00
20 29 - 29 does anybody understand that
7:06
right -10 - 19 is -29 thank
7:10
you what about -10 + 9 2929 why do you
7:16
think that this both of them at the same
7:18
time because they're both the same right
7:21
I want to show you that this and these
7:22
are the same thing same the same thing
7:24
right we're saying technically the same
7:26
thing when we do this and that I'm
7:29
saying the same thing okay I want you to
7:32
get that now what is 7 - 20 say that
7:40
um
7:43
mhm yeah let's use it
7:48
oh is not a negative it's
7:51
7 - 20 plus 20 so 7 plus 27 No 7 + -20
7:58
would be what wait oh
8:01
it's negative it's not a negative yes it
8:05
is a negative yes it is 20 is a
8:10
negative-3 my brain I'm telling you guys
8:12
you have $7 how is it no but why would
8:15
that be a negative okay it looks like a
8:17
subtraction sign it's a subtraction
8:19
right it's 7 minus 20 right you you have
8:23
$7 and you spend 20 can you do that you
8:27
have you short right I was 13
8:30
$13 okay now what is -7 -
8:37
107 -7 thank
8:39
you
8:41
-7 now this is the one that you all like
8:44
right 12 -
8:46
-6
8:50
Nate 12
8:54
--6 18 18 why because two have two
8:58
negatives turn into what positive so
9:01
that's 12 + 6 right that's 18 better -6
9:06
actually no better call it -6
9:18
-9 three three right because this is -6
9:22
+ 9 because this two turn into a
9:24
positive so you get pos3 all right so
9:28
I'm glad you guys are getting it so
9:29
let's continue we're going to do some
9:31
more work
#Mathematics