How to find the solution (x,y)

[homevolend]

Homework Statement

The solution (x,y) of the system equations define by x-y=1 and 2x+y= -4 is what

Homework Equations

The Attempt at a Solution

I found x and y intercepts of these and plotted it but don't know what it means by finding the solution.

 

[jbunniii]

Finding a solution means finding value(s) of x and y that satisfy both equations simultaneously.

Geometrically, it means finding the intersection of the two lines given by the equations you listed.

Why don't you start by choosing one of the equations, and solving for y in terms of x. Then try substituting that into the other equation.

 

[homevolend]

y =

2 [x-y=1]
-1 [2x+y=-4]

2x-2y=2
-2x-y=4
--------
-3y=6
y=-2


1[x-y=1]
1[2x+y=-4]

x-y=1
2x+y=-4
--------
-x=-3
x=3 I think I did x wrong somehow but don't know what, but I think I did y right.


like that??

 

[jbunniii]

y =

2 [x-y=1]
-1 [2x+y=-4]

2x-2y=2
-2x-y=4
--------
-3y=6
y=-2


1[x-y=1]
1[2x+y=-4]

x-y=1
2x+y=-4
--------
-x=-3
x=3 I think I did x wrong somehow but don't know what, but I think I did y right.


like that??

Everything looked OK until this part:

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

This is wrong because x + 2x does not equal -x.

 

[ehild]

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

You can add the equations: y will cancel.

ehild