Simultaneous equation

davey2015

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Jun 27, 2015
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Simultaneous equation help if you dont mind guys


this is what i have so far.

Question:

3x = 2y
4x + y + 11 = 0

What i done so far:

9x = 6y (Times 3)
8x + 2y + 22 = 0 (times 2)

okay, so now i take one from another and i get:

9x = 6y -
8x + 2y + 22 = 0
-----------------------------
1x -2y -22 = 6y

now i plus 2y on both sides to simplify, so now i have:

x -22 = 8y

any help where i am going wrong???
 
Simultaneous equation help if you dont mind guys

this is what i have so far.

Question:

3x = 2y
4x + y + 11 = 0

What i done so far:

9x = 6y (Times 3)
8x + 2y + 22 = 0 (times 2)
Is there any particular reason you chose these multipliers? One, they're big and, two, they don't offset; 9x won't cancel off an 8x, and 6y won't cancel off a 2y. Turning the x-terms into 12's would have made better sense, if that's the variable you're trying to get rid of.

Instead, try picking useful multipliers. You have a 2y and a 1y. Rearrange and multiply to get rid of these:

. . .Rearrange:
. . . . .3x - 2y = 0
. . . . .4x + 1y = -11

. . .Multiply:
. . . . .3x - 2y = 0
. . . . .8x + 2y = -22

Now add down. What do you get? ;)
 
While I prefer Stapel's method, as it seems easier and more straightforward, I just want to point out that your method will also work, if you continue on. As I see it, you just stopped five feet short of the goal.

You have x - 22 = 8y. So add 22 to both sides, and then x = 8y + 22. Now that you've got a value for x in terms of y, substitute that value back in to either equation (the first one's simpler to work with) and solve.
 
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