Thread: Linear Equations through Elimination?

NO idea how to do this. Can someone please help me?

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

y=1

x=4

How did you get that?

Originally Posted by SoobadatMath.

NO idea how to do this. Can someone please help me?

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

add the two equations, term for term ...

-x + 3y = -1
x - 2y = 2
------------
0 + y = 1 ... note that the x terms cancel

now sub 1 in for y in either equation and solve for x.

So then x + 3y = -4
y + x = 0
???????????????????

Originally Posted by SoobadatMath.

So then x + 3y = -4
y + x = 0
???????????????????

What are you doing ?

You were told that y = 1.
So replace the y with 1 in one of the equations, then solve for x.

Originally Posted by SoobadatMath.

So then x + 3y = -4
y + x = 0
???????????????????

new system ...

x + 3y = -4
y + x = 0

multiply every term in the second equation by -1 ...

x + 3y = -4
-x - y = 0
-------------

add 'em up and solve.

x + 3y = -4 [1]
y + x = 0 [2]
If that's a new system, then from [2]: y = -x
So [1]: x - 3x = -4