Question

*MEDAL*

Solve the system by substitution.

Choices:
(3, 5)
(-5, -3)
(-3, -5)
(5, 3)

Answer 1

The first equation looks interesting. Why not solve that for 'y' and substitute into the 2nd equation?

Answer 2

Alright, one moment! this is new material and I'ma bit confused :/

Answer 3

y = -5.5 for the top.

Answer 4

Doesnt sound right...

Answer 5

?? You cannot get a numerical answer with only one equation. Try again, and don't lose your 'x', this time.

Answer 6

2x + y =-11
-1 -1
_____________
2x = -12
x = -6??

Answer 7

Why are you subtracting 1? There are no '1's in there.

2x + y = -11

Subtract something that is there. Subtract 2x

y = -11 - 2x

Answer 8

So now do I add 2 to each side..?

Answer 9

Substitute the y value found above into equation 2 and let me know what you get.

Answer 10

Okay, @ranga
I don't really know how :l What do you mean? Subract 2 by what exactly?

Answer 11

y = -11 - 2x
+2 +2

??

Answer 12

First copy the second equation as is here.

Answer 13

Equation 1) 2x + y = -11
Equation 2) 3x - 4y = 11

Solve Equation 1) for y

y = -11 - 2x

Substitute this value for y into Equation 2

Original Equation 2) 3x - 4y = 11
Substituted Equation 2) 3x - 4(-11-2x) = 11

Now, the task is to solve that equation for x.

Do NOT add or subtract anything that doesn't exist. If it says 3x, you cannot add 3. The term is 3x. All or nothing!

Answer 14

y = -11 - 2x
+2 +2

That is not meaningful. There is no 2 in there to manipulate. No one ever showed you anything like that. It doesn't work for anything. If we were to manipulate, it would have to be with 2x, not 2. However, there is no more manipulation. We are done. It is time to substitute.

Answer 15

3x - 4(-11-2x) = 11
3x + 44 - 2x + 11
(Combine Like Terms)
1x + 44 = 11
- 44 -44
____________________
x = -33

Yup. I did wrong again.

Answer 16

Nvm, I suck a math. Thanks anways.

Answer 17

Don't give up that easily. -4(-11-2x).
You have to multiply each term within the parenthesis by -4 not just the first one. That is where your error is.

Answer 18

3x - 44 + 8x = 11?

Answer 19

Good. Add up the x terms.

Answer 20

11x - 44 =11

Answer 21

Good. We need to isolate x on the left. So add 44 to BOTH sides to get rid of the 44 on the left.

Answer 22

11x = 55

Answer 23

Good. Divide BOTH sides by 11.

Answer 24

x = 5? :D

Answer 25

Yes!
Now solve for y.
Earlier we had y = -11 - 2x
Put x = 5 and solve for y.

Answer 26

y = -21?

Answer 27

oh wait!

Answer 28

nvm...I thought it was something else. I did something wrong :l

Answer 29

But I do know the answer will be (5, 3).

Answer 30

Wait we have to go back a few steps. You changed the sign and I did not notice it.

From equation 1 you had y = -11 - 2x

Equation 2 is: 3x - 4y = 11

We substitute the y = -11 - 2x

3x - 4(-11 - 2x) = 11
3x +44 + 8x = 11 (initially you had +44 but later you switched it to -44 and I did not notice it)
Anyway simplify:
11x + 44 = 11
Subtract 44 from both sides
11x = 11 - 44 = -33
Divide both sides by 11
x = -3

Put x = -3 in y = -11 - 2x
y = -11 -2(-3) = -11 + 6 = -5

So x = -3 and y = -5 is the answer.

Answer 31

Thank you so much! :DDD