Question

Solve the systems using substitution.

6x + 2y = 0
4x + y = -1

3x + 2y = -4
x + 2y = -8

5x - 4y = 14
x - 2y = -2

x + 3y = -4
4x + 5y = 5

x + 3y = -5
2x - y = 18

Answer 1

y=-4x-1
now substitute (-4x-1) for y on the equation: 6x+2y=0

Answer 2

You have 6x + (2(-4x-1)) = 0

Answer 3

Then 6x - 8x - 2 = 0

Answer 4

Therefore -2x = 2
---- ---
-2 -2

x = -1

Answer 5

i dont understand substitution

Answer 6

Then to find y substitute -1 for x
6x + 2y = 0
6(-1) + 2y = 0
-6 + 2y = 0
2y = 6
y = 3

Answer 7

Therefore x = -1 and y = 3
Now you can check by substitution of x and y to see if is true

Answer 8

6x + 2y = 0
6(-1) + 2(3) = 0
-6 +6 = 0
0=0 this is true

Answer 9

The other equation:
4x + y = -1
4(-1) + 3 = -1
-4 + 3 = -1
-1 = -1 true then is correct

Answer 10

@ivettef365 what is x + 2y = -8 ?

Answer 11

?

Answer 12

on this one I would live x by itself
x = -2x-8

Answer 13

Now substitute x by (-2x-8) on equation 3x + 2y = -4

Answer 14

3(-2x-8)+2y=-4?

Answer 15

Sorry I meant x = -2y - 8

Answer 16

2(-2y-8) + 2y = -4

Answer 17

oh okay :)

Answer 18

then just solve it? @ivettef365

Answer 19

right, if you get stuck let me know

Answer 20

okay!

Answer 21

@ivettef365 2(-2y-8) + 2y = -4
-4y - (-16) + 2y = -4
-4y+16 + 2y = -4
-2y +16 = -4
-2y = -20
y=-10 ?

Answer 22

then: 3x + 2y = -4
3x + 2(-10) = -4
3x+-20=-4
3x=-24
x=-8 ?

Is this right for number two?

Answer 23

I got for x = 2 and for y = -5

Answer 24

You put 2 instead of 3, it should have been
3(-2y-8)+2y = -4

Answer 25

-6y-24+2y=-4
-4y-24 = -4
-4y = 20
y = -5

Answer 26

Now that you know y = -5 find x
use the most simple one
x - 2y = -8
x -2(-5) = -8
x + 10 = -8
x = 2

Answer 27

oohh
but the first part is right?

Answer 28

Try doing the 3rd problem

Answer 29

x = 2y - 2

Answer 30

Substitute (2y-2) for x on 5x - 4y = 14

Answer 31

Alright! x - 2y = -2
x=2y-2
5(2y-2) - 4y = 14

Answer 32

10y-10 - 4y=14?

Answer 33

10y+10-4y=14 *

Answer 34

14y +10=14
14y=4
y=3.5? @ivettef365

Answer 35

10y-4y-10 = 14
6y = 14 +10
6y = 24
y= 4

Answer 36

mind if i work the other two with you?

Answer 37

5x - 4(4) = 14
5x-16=14
5x=30
x=6

Answer 38

correct

Answer 39

Now to check you can do
5(6) - 4(4) = 14
30 - 16 = 14
14 = 14 correct

Answer 40

The other one
x - 2y = -2
6 - 2(4) = -2
6 - 8 = -2
-2 = -2 correct

Answer 41

4x + 5y = 5
5y+4x=5?

Answer 42

I need help with the second equation for both problems :/ I'm not sure how to convert them

Answer 43

This one you use
x + 3y = -4

Answer 44

Convert to x = -3y-4

Answer 45

wheres the 5...?

Answer 46

err for 4x + 5y = 5. i thought we convert the second equation first

Answer 47

It doesn't matter which one you convert, use the easiest one to convert

Answer 48

Now substitute (-3y-4) for x on equation
4x + 5y = 5

Answer 49

do you mean for y...?

Answer 50

For x

Answer 51

You do the following
4(-3y-4) + 5y = 5

Answer 52

4(-3y-4)+5y=5
-12y +5y = 5

Answer 53

-7y = 5

Answer 54

-12y -16+5y = 5

Answer 55

You missed the -16

Answer 56

where is the -16 come from? i thought it was 4*-4

Answer 57

4(-3y-4)+5y = 5
-12y-16+5y = 5 (you multiply the 4 by -3y and by -4)

Answer 58

4*-4 = -16

Answer 59

-12y -16+5y = 5
-12y+5y-16=5
-7y-16=5
-7y=21
y=-3?

Answer 60

correct

Answer 61

yay! one more ^_^

Answer 62

Now solve for x

Answer 63

i keep forgetting that!
4x + 5y = 5
4x+5(-3) = 5
4x+-15=5

Answer 64

or -15+4x=5?

Answer 65

When you already have a value, like in this case you have the value for y = -3
try to use the easiest equation to find the other value

Answer 66

In this case is x + 3y = -4
x + 3(-3) = -4

Answer 67

x + 3y = -4
x+3(-3-- you beat me to it :P

Answer 68

x + 3(-3) = -4
x+-15=-4

Answer 69

x - 9 = -4

Answer 70

+3 * -3 = -9

Answer 71

yeah.. my calculator said -15? :|

Answer 72

x-9=-4
x=5

Answer 73

correct, then you have
x = 5 and y = -3
you can do the checking if you want to

Answer 74

one more question :D i need you to convert it for me xD

Answer 75

The top one is easier to convert

Answer 76

You have x + 3y = -5

Answer 77

need to transfer the 3y to the other side so the x stays by itself,
therefore to transfer you need to switch sign.

Answer 78

3y-x=-5..?

Answer 79

It would be as follows:
x + 3y = -5
x = -3y -5

Answer 80

yeah s: i'm not good at that...
2(-3y -5) - y = 18

Answer 81

That is good, what is the next step

Answer 82

-6y - (-10) - y = 18

Answer 83

-6y-10-y = 18

Answer 84

-6y-y-10=18

Answer 85

-7y-10=18

Answer 86

-7y=28
y=-4

Answer 87

Good job

Answer 88

x + 3y = -5
x + 3(-4) = -5

Answer 89

x+-12=-5

Answer 90

did you get the answer

Answer 91

i was making sure that was right, haha.

Answer 92

x+-12=-5
x=7?

Answer 93

Good job

Answer 94

thank you so much!!

Answer 95

yw :)