Help with solving a system through elimination.

[ochocki]

6x - 3y = -3
4x + 5y =-9

I will show the steps I have been taking, maybe you will be able to point out where I am making an error.

First I made the y variable opposite through multiplication

5(6x -3y) = 5(-3)
3(4x+5y) = 3(-9)

30x - 15y = -15
12x +15y = -27
-----------------------------
42x = -42
___ ___
42 42

X=-1

I then plug in -1 to the x variable of the second equation to obtain the value of y.

4(-1) + 5y = 3
-4 + 5y = 3

I then add 4 to both sides of the equation and isolate the y.

5y = 7
__ __

5 5

y=1.4

This is really frusturating because the solution set (-1, 1.4) doesn't work, i'm also sure that both of the ordered pairs have to be whole numbers. I have looked at the original equation and I believe that the actual solution is (-1, -1) why can't I get that?

If anyone can identify where I am making an error I would be greatly appreciative.

 

[galactus]

6x - 3y = -3
4x + 5y =-9

I will show the steps I have been taking, maybe you will be able to point out where I am making an error.

First I made the y variable opposite through multiplication

5(6x -3y) = 5(-3)
3(4x+5y) = 3(-9)

30x - 15y = -15
12x +15y = -27
-----------------------------
42x = -42
___ ___
42 42

X=-1

I then plug in -1 to the x variable of the second equation to obtain the value of y.

4(-1) + 5y = -9

I think you, inadvertently, wrote 3 instead of 9
-4 + 5y = 3

I then add 4 to both sides of the equation and isolate the y.

5y = 7
__ __

5 5

y=1.4

This is really frusturating because the solution set (-1, 1.4) doesn't work, i'm also sure that both of the ordered pairs have to be whole numbers. I have looked at the original equation and I believe that the actual solution is (-1, -1) why can't I get that?

If anyone can identify where I am making an error I would be greatly appreciative.

 

[ochocki]

Ahh, a simple clerical error. I just don't understand how I made the same error over and over again.

Thank you very much.