Question

-3x-y=9 2x+y=6
-x-2y=0 3x+y=0
tell me how to do one and i will try to do the other one..(use the substitutional method)

Answer 1

i mean:

3x-y=9 2x+y=6
x-2y=0 3x+y=0

Answer 2

3x-y=9 2x+y=6

I assume that is one question.

The easiest thing to get by itself is "y" in the 2nd part. If I have 2 xylophones and one Yankee, the way to get the Yankee by himself is to simply take away the 2 xylophones.
2x+y=6
y=6-2x

Now we know what the "yankee" is. He is 6 minus 2 xylophones.

Let's look at the other equation.

3x-y=9
3 xylophones minus the yankee equals nine.

So 3 xylophones minus (6 minus 2 xylophones) equals 9.

3x- (6-2x) = 9
3x - 6 + 2x = 9
Let's add the xylophones together.
5x - 6 = 9
Put the 5 xylophones by themselves. Easiest way is to add the -6 and 6.
5x = 15

If 5 xylophones are worth 15 dollars, how much is one worth?

15 divided by 5 is 3.

A xylophone is worth $3.
How much is the Yankee worth?

3x-y=9

We have 3 xylophones and they are worth $3. 3x3 = 9.

$9 minus the price of the yankee is ... Well ... $9 according to this.

9-y = 9

The yankee must obviously be worth nothing.

Y=0
X=3


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