Not getting it - step by step please?

Question

x - y = 3
2x - y = -1

is this right
2x - y = 2

then what? lol

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2x + 4y = 10
3x - 2y = -9

Answer 1

What you want to do is make one variable be the opposite of the one below it then add the two rows together. You could for example multiply your first equation by -1 making it

-x + y = -3 then add it to
2x - y = -1 getting

x = -4. Then plug this in for x to get y: -4 - y = 3; add 4 to both sides -y = 7 so y = -7

Next one, multiply the second row by 2 getting

6x - 4y = -18 then add it to the first
2x + 4y = 10 getting

8x = -8 which when you divide by 8 gives x = -1. Then plug it in like before to get y

Answer 2

You want to add the equations together so that one of the variables disappears. So in the first case multiple the first equation by -1 to get:

-x + y = -3

Now add that equation to the second one, and the y variable will disappear.

-x + y = -3
2x - y = -1
--------------
x = -4

Now that you know x = -4, just plug it into either one of the equations to get the value of y

x - y = 3
-4 - y = 3
-y = 7
y = -7

So x = -4 and y = -7

For the second equations, do the same thing. Multiply the second equation by 2, and that will allow you to add the equations together to get rid of the y variable.

2x + 4y = 10
6x - 4y = -18 (multiplied the second equation by 2).

Now add them together

8x = -8

Now solve for x

x = -1

Now plug in x into one of the original equations to get y

2x + 4y = 10
-2 + 4y = 10
4y = 12
y = 3

So x = -1 and y = 3

Answer 3

1) subtract the first from the second:
2x - y = -1
-x + y = -3
x = -4, so if x-y =3 then y = -4-3 = -7

2) double the second and add:
2x + 4y = 10
6x - 4y = -18
8x = -8, so x = -1. From first -2 + 4y = 10, and y = 3

Answer 4

You must make either the x's or y's disappear. Let's make the y's disappear.
Multiply the top equation by -1 then add the equations together.
-x + y = -3
2x - y = -1
ADD THEM
1x + 0y = -4
THEREFORE
x = -4