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Home > Education > High School   »   alg 2

 
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Old Dec 17, 2006, 02:39 PM
bratzdoll3
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alg 2

whats the x coordinate of the solution of the following system od linear equations?
-3x-5y=-23
2x-4y=-14

is the answer

a. 4
b. 0
c. -4
d. -1
e. 1

how do you do this?

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Old Dec 17, 2006, 02:51 PM   #2  
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for simultaneous equations, you need to multiply up so you can get rid of a variable.

In this case you want X, so we need to get rid of y

If you multiply all terms in your top equation by 4 and all terms in your bottom equation by 5, you will have 2 equations both with -20y in them.

You can then subtract the two equations, ending up with 0y and an amount of x, it's then simple algebra to solve for x.

Let me know how you get on!

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Phrase_shifter agrees: helpful but not realli try using numbers next time. OK?
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Old Dec 17, 2006, 08:11 PM   #3  
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If I have done my math correct…..

-3x-5y=-23
2x-4y=-14

-5y=-23 + 3x
-4y =-14 – 2x

y = 4.6 - 0.6x
y =3.5 + 0.5x

3.5 + 0.5x = 4.6 - 0.6x
0.6x + 0.5x = 4.6 – 3.5
1.1x = 1.1
x = 1

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Phrase_shifter agrees: it uses a simple and les known solution mathod (note: i-m east european)
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Old Dec 18, 2006, 03:27 AM   #4  
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ewww dividing.

multiplying up is your friend.
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Old Dec 18, 2006, 10:31 PM   #5  
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-5y=-23 + 3x
x4
= -20y = -92 + 12x


-4y =-14 – 2x
X 5
= -20y = -70 – 10x


-92 + 12x = -70 – 10x
12 x + 10 x = -70 + 92
22x = 22
x = 1

I still get x=1
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Old Dec 19, 2006, 04:10 AM   #6  
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Well yes... I'm not saying you're wrong
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Old Dec 19, 2006, 10:53 AM   #7  
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lol
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