Question

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

2x + y = 9
−x − y = −8

−8 + y

−8 − y

8 + y

8 − y

Answer 1

Do you understand what the question asks for?

Answer 2

If you do the answer is simple.

Answer 3

This is the 2nd equation −x − y = −8
You want to use this to express x than use it to solve the 1st equation.
For this you need to get an equation like x=something with only y in it.

Answer 4

−x − y = −8
From this express it like x=.....

Answer 5

Yes I understand what the question is asking for, what I don't understand is the outcome after O divide by -y.

Answer 6

You dont have to divide by y

Answer 7

(the equation divided by -y)

Answer 8

Sorry -1

Answer 9

there is no division!
-x-y=-8
There is only subtraction in this equation

Answer 10

take the -y first to the other side. So that the x bit is on one side and the y bit is on the other

Answer 11

If you want to cancel a subtraction what do you do?
What is the opposite of it?

Answer 12

Addition

Answer 13

-x-y+y=?

Answer 14

-y=-8 + y

Answer 15

-x=-8+y

Answer 16

but you need +x not -x now what to do?

Answer 17

What operation changes all the signs but leaves the numbers otherwise?

Answer 18

Divide-x? Which would be x= 8-y?

Answer 19

Nope.
You multiply by -1

Answer 20

If you multiply something with 1 you get the number itself.
If you multiply by -1 that you get the numbers opposite

Answer 21

And when you see x and y they are just numbers, unknown numbers

Answer 22

So what happens with -x=-8+y if both sides are multiplied by -1?

Answer 23

x=8-y?

Answer 24

Yep!

Answer 25

Yea!!!!!

Answer 26

Hope it cleared up a bit of confusion

Answer 27

It really did thanks for taking out the time, I really appreciate it!