SOLUTION: I am confused on how to solve systems using equations. here is the problem: x-2y=-8 y= -x - 2 so far i have tried this: x+-2y=-8 -2 -2 x=8-2y 2y=-8 +2 i am confu

Question 69915: I am confused on how to solve systems using equations.
here is the problem:
x-2y=-8
y= -x - 2
so far i have tried this:
x+-2y=-8
-2 -2
x=8-2y
2y=-8 +2
i am confused on what i am doing wrong.
can you help?
thanks.
Found 2 solutions by jim_thompson5910, ptaylor:
Answer by jim_thompson5910(35256) (Show Source): You can put this solution on YOUR website!
I'm not sure I'm reading your notation right, but I'll see what you're doing wrong. You have 2 equations x-2y=-8 and y= -x - 2 given to you, so you can use one equation to solve for another. For instance, since y=-x-2 you can substitute that y value for the y value in the first equation
Equation 1
Equation 2Plug this y into the y of the first equation
Equation 1 The red box is where the y was originally
Solve for x

Use this x value to solve for y

Answer by ptaylor(2198) (Show Source): You can put this solution on YOUR website!
Substitution seems to be the most straightforward way of solving this system:
(1) x-2y=-8
(2) y= -x - 2
Look at eq (2)
y=-x-2
-y=x+2
-2y=2x+4-----------substitute this into (1) and we get:

x+2x+4=-8 subtract 4 from both sides
3x=-8-4
3x=-12 divide both sides by 3
x=-4
substitute x=-4 into (2) and we get:
y=4-2
y=2
CK
(1) x-2y=-8
-4-2(2)=-8
-8=-8
(2) y=-x-2
2=4-2
2=2
Another approach, similar to what you were doing, is as follows:
(1) x-2y=-8
(2) y=-x -2 re-arrange by subtracting y and adding 2 to both sides:
(1) x-2y=-8
(2) y-y+2=-x-y-2+2 collecting like terms:
(1) x-2y=-8
(2) 2=-x-y or -x-y=2
(1) x-2y=-8
(2) -x-y=2

Add (1) and (2)
-3y=-6 divide both sides by -3
y=2
substitute y=2 in (1)
x-2*2=-8
x-4=-8 add 4 to both sides
x=-4

Hope this helps-----ptaylor

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