Question

Solve the following system of equations for x.



- 3x + 7y = 2

- 2x - 3y = - 4


A. http://diagnostic.achievementseries.com/cdn//1/_graphics_math_13085f/12223589-ea44-4b1e-a0b2-1095ae81db3b.gif
B. http://diagnostic.achievementseries.com/cdn//1/_graphics_math_13085a/7ab02291-e365-4ff9-89cd-9ee8a60f4ad8.gif
C. http://diagnostic.achievementseries.com/cdn//1/_graphics_math_13085c/d634628c-1794-422e-a57c-8313ece11b84.gif
D. http://diagnostic.achievementseries.com/cdn//1/_graphics_math_13085b/20be9799-970d-4007-9a8d-0bd7fb2f6171.gif

Answer 1

We can multiply the first equation by 3, and the 2nd by 7.

Answer 2

Can you do that? @chycora

Answer 3

1. solve for x or y for the first or second equation
2. sub what you determined x or y to be equal using the first equation into the other equation
3. the equation should only be in terms of one of the variables solve for that variable
4. plug that variable into one of your equations and find the other

Answer 4

yes so -3x * 2 right @iGreen

Answer 5

* 3

Answer 6

We're multiplying by 3, not by 2..

Answer 7

for example

x + 3y = 3
x + 4y = 2

1.
x = 3 - 3y

2.
x + 4y = 2
(3 - 3y) + 4y = 2
3 - 3y + 4y = 2
y = -1

3.

x + 3y = 3
x + 3(-1) = 3
x = 6

Answer 8

- 3x + 7y = 2

-3x * 3
7y * 3
2 * 3

Answer 9

Can you multiply those?

Answer 10

o ok so -3x *3 = -9x
7y * 3= 21y
2 * 3 = 6

Answer 11

Correct, so we have:

-9x + 21y + 6

Answer 12

Now multiply the 2nd equation by 7.

Answer 13

- 2x - 3y = - 4

-2x * 7
-3y * 7
-4 * 7

Answer 14

ok so -2x * 7 = -14x
3y * 7 = 21y
-4 * 7 = -28

Answer 15

That's -3y

Answer 16

So it would be -21y

Answer 17

So we have: -14x - 21y = -28

Answer 18

o ok srry i thought that was a subtracting sign

Answer 19

Now add the two equations together.

Answer 20

It is, but it acts as a negative sign too.

Answer 21

o ok

Answer 22

-14x - 21y = -28
-9x + 21y + 6


Add them.

-14x + -9x = ?
-21y + 21y = ?
-28 + 6 = ?

Answer 23

Btw, we multiplied these equations by a certain number to cancel out the y-value's..so we can solve for the 'x'.

Answer 24

-14x + -9x = -23
-21y + 21y = 0
-28 + 6 = -22
and ok

Answer 25

That's actually -23x

Answer 26

is the anser \[x= -\frac{ 22 }{ 23? }\]

Answer 27

We keep the variable.

Answer 28

right i kn

Answer 29

Close.

That gives us:

-23x = -22

Divide -23 to both sides

Answer 30

i gt \[-1 \frac{ 1 }{ 22? }\]

Answer 31

No.

x = -22/-23

Answer 32

Which is the same as 22/23

Answer 33

so no negative sign

Answer 34

Nope.

Answer 35

so there is a negative sign

Answer 36

No..you're correct..there's no negative sign.

Answer 37

o ok