Question

For the following system, if you isolated x in the first equation to use the Substitution Method, what expression would you substitute into the second equation?

−x − 2y = −4
3x + y = 12

−2y − 4
2y − 4
2y + 4
−2y + 4

Answer 1

@BenLindquist @Shadow

Answer 2

@Pixel

Answer 3

Okay, first do you know how to isolate x?

Answer 4

i might, but i probably forgot. if u start it i will probably be like 'wait ik this!'

Answer 5

\(−x − 2y = −4\)

What is the opposite of subtracting 2y?

Answer 6

sorry, internet. that would be adding 2y

Answer 7

Right so add 2y on both sides
\(-x-2y=-4\)

Answer 8

-2y + 2y = 0 so that is cancled out leaving -x = -4.

Answer 9

−x−2y=−4
Step 1: Add 2y to both sides.
−x−2y+2y=−4+2y
−x=2y−4
Step 2: Divide both sides by -1.
−x
−1
=
2y−4
−1
x=−2y+4
Answer:
x=−2y+4

Answer 10

-4 + 2y would by 2y.

Answer 11

Right on

Answer 12

be*

Answer 13

@RichardWatterson7 Please refrain from giving out direct answers.

Answer 14

💁👌

Answer 15

is there more to is? :/

Answer 16

\(-x = -4+2y\)

We need to get rid of the - in front of the x

What is the opposite of multiplying -1?

Answer 17

dividing -1

Answer 18

Right, so do it on both sides

Answer 19

could u say the problem again so i can see it? every time i try to copy it it shoots me back down here and i cant see it

Answer 20

\(−x=−4+2y\)

Answer 21

thx
-1 divided by -x would cancel it out leaving it as just X

Answer 22

meaning it is now x = - 4 + 2y

Answer 23

@dude im stuck here lol

Answer 24

You were supposed to divide -1 on both sides

So divide `-4+2y` by -1

Answer 25

-4 divided by -1 would by normal 4

Answer 26

Yes

Answer 27

do we do 2y divided by -1 or no? :/

Answer 28

Yes do 2y divided by -1

Answer 29

ok, that would be -2y

Answer 30

Correct, so now we have
\(x=4-2y\)

Answer 31

Lets get the second equation given to us from the question

\(3x + y = 12\)

Answer 32

Now substitute the newly found equation into the second equation, so you know how to do that?

Answer 33

no i donut :/

Answer 34

or i might lol

Answer 35

Try it

Answer 36

yea no i got nothin lol

Answer 37

Okay so we have the equations
\(3\color{red}{x}+y=12\)
and
\(\color{red}{x}=4−2y\)

Answer 38

\(3\color{red}{x}+y=12\)
\(3\boxed{\color{red}{4-2y}}+y=12\)

Do you see how I did that?

Answer 39

i want to say that i do, but i dont :(

Answer 40

Let me try to color-code it




If you cannot still understand it, tell me which part confuses you

Answer 41

oh ok. no i got it now. what next?

Answer 42

Distribute the 3

Answer 43

3 x 4 is 12 and 3 x 2 is 6 + y would be 6y so it is now 12 - 6y + y = 12

Answer 44

Right on :P

Now combine the y's
\(12 - 6y + y = 12\)

Answer 45

12 - 6y + y = 12
y - y = 0
12 - 6 = 12 ( i think i did that right)

Answer 46

Nah u have to add well no subtract the y's then what do u get

Answer 47

Not quite

You want to first combine the terms with the y

Answer 48

Shut up Richard. (those who have watched tommy boy will get it)

Answer 49

y = 1 right?

Answer 50

yea it does

Answer 51

ok thx Richard.

Answer 52

np math is my favorite subject sooo

Answer 53

yea i dont freakin get it

Answer 54

pretty much do 6y-y or 6y-1y and what do u get

Answer 55

5y

Answer 56

yea now what do u have

Answer 57

12 - 5y = 12

Answer 58

12 - 12 = 0
y = 5

Answer 59

No, subtract the 12 and what do u get

Answer 60

Do −5y+12−12=12−12 and what do u get