#### lost and found

##### New member

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- Jan 13, 2006

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- Thread starter lost and found
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- Joined
- Jan 13, 2006

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First one looks like this:

Code:

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- Joined
- Jan 13, 2006

- Messages
- 2

yes i just don't really know how to solve thoese equations... i mean there are two varuables...

4x-y=4 andlost and found said:yes i just don't really know how to solve thoese equations... i mean there are two varuables...

2y=3x+17

4x - y = 4 [1]

3x -2y= -17 [2] : follow that?

***Multiply [1] by -2:

-8x + 2y = -8 [1]

3x - 2y = -17 [2]

Now add [1]+[2]:

-5x = -25

Can you finish it?

***we could multiply by 2, then subtract the 2 equations: same result.

The intent is to rearrange so we can eliminate one variable.

Here's an example:

3x + 2y = 16 [1]

5x - 3y = -5 [2]

Multiply [1] by 3 and [2] by 2:

9x + 6y = 48 [1]

10x - 6y = -10 [2]

See what happens to the y terms?

Now add the 2 equations:

19x = 38

x = 2

Now substitute x = 2 in [1]

3(2) + 2y = 16

6 + 2y = 16

2y = 16 - 6

2y = 10

y = 5

Able to follow that?

Yes? Ok then, try this one:

5x + 7y = 31 [1]

9x - y = 15 [2]