View Full Version : Solve 0.3x - 0.y = 4, 0.2x + 0.3y = -37/17 by elimination
dsj1023
10-05-2008, 05:33 PM
I am trying to solve this problem using the elimination method when the answer is a fraction
.3x - .2y = 4
.2x + .3y = -37/17
I took the top equation times 3 and the bottom equation times 2 so that the y's would subtract out. That left me with:
1.3x = 7 11/17
From there everything got messy and I got lost. This is my first time posting a problem on here so if I didn't do something right in posting please let me know!
galactus
10-05-2008, 05:39 PM
First, shed the decimals by multiplying by 10:
3x-2y=40
2x+3y=\frac{-370}{17}
Multiply the first row by 2 and the second row by -3:
6x-4y=80
-6x-9y=\frac{1110}{17}
Now, add them and get rid of the x value:
-13y=\frac{2470}{17}
There's a start.
dsj1023
10-05-2008, 05:50 PM
OK I took your start and here's what I did:
6x - 4y = 80
-6x - 9y = 1110/17
-13y = 2470/17
y = -11 39/221
3x - (2)-1139/221 = 40
3x - (-22 78/221) = 40
3x + 22 78/221 = 40
3x = -62 78/221
x = -20 520/663
Am I way off base here? Thanks for replying as quickly as you did!
galactus
10-05-2008, 05:55 PM
Please, try not use mixed numbers. Keep them in improper fraction form.
Try y again. Shouldn't that be y= -190/17. Or, if you must, 11 3/17
dsj1023
10-05-2008, 06:02 PM
I keep getting the same thing for y - I'm not coming up with the answer you got.
galactus
10-05-2008, 06:11 PM
-13y=\frac{2470}{17}
y=\frac{-2470}{221}=\frac{-190}{17}
dsj1023
10-05-2008, 06:18 PM
OK I figured it out - so x then equals 100/17.
Thanks!
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