Solve via elimination

• May 26th 2011, 09:05 PM
jay1
Solve via elimination
I think I am doing this problem wrong. To solve by elimination:
0.3x-0.2y=4 and 0.4x +0.3y=-1. After changing to integers, I multiplied the 1st equation by 4 and the second by 3 ending up with 8x-11y=17. I do not know where to go from here, or if I did this correctly...
• May 26th 2011, 11:16 PM
borophyll
You have done the first step successfully: multiplying the first equation by 4 gives you 1.2x - 0.8y =16, and multiplying the second equation by 3 gives you 1.2x + 0.9y = -3.

Now, apply the elimination method. I'm not sure where you got the result you have. If you are having trouble understanding the elimination method, try Googling for "solve equations by elimination"
• May 28th 2011, 01:16 PM
jay1
Thank you. Just to be sure: I now add both equtions. Then, how do I solve for Y? Do I divide each side? This is where I'm unsure...
• May 28th 2011, 01:43 PM
Quote:

Originally Posted by jay1
I think I am doing this problem wrong. To solve by elimination:
0.3x-0.2y=4 and 0.4x +0.3y=-1. After changing to integers, I multiplied the 1st equation by 4 and the second by 3 ending up with 8x-11y=17. I do not know where to go from here, or if I did this correctly...

You should review how you ended up with 8x-11y=17.

To solve by elimination, first decide whether or not you want to
eliminate x or y.
Having eliminated one, you will find the value of the other.

3x-2y=40 after multiplying both sides by 10.
4x+3y=-10

If we choose to eliminate y, we can obtain -6y on the first line
and +6y on the second line.

How do arrive at that ?
• May 28th 2011, 06:50 PM
jay1
Quote:

You should review how you ended up with 8x-11y=17.

To solve by elimination, first decide whether or not you want to
eliminate x or y.
Having eliminated one, you will find the value of the other.

3x-2y=40 after multiplying both sides by 10.
4x+3y=-10

If we choose to eliminate y, we can obtain -6y on the first line
and +6y on the second line.

How do arrive at that ?

By multiplying the top equation by -2 and the bottom by 3. I then end up with -1x = 100. Is this right?
• May 29th 2011, 01:56 AM