Remember that we can check our answer by putting it into ALL of the original equations:

1 ) x + 2y - 5z = -11 and 2 ) 4x - 3y + 2z = 11 and 3 ) -3x + 5y + 3z = 8

2 + 2 ( 1 ) - 5 ( 3 ) = -11 ... 4 ( 2 ) - 3 ( 1 ) + 2 ( 3 ) = 11 ... -3 ( 2 ) + 5 ( 1 ) + 3 ( 3 ) = 8 ... All three work!
 


YOUR TURN:

Do the first problem, but start by ditching the x...  You'd better get the same answer I did!

2x - y + 5z = 4

x + y + z = -1

-3x + 2y - 6z = -7

 

Now, do the problem again, but start by ditching the z:

2x - y + 5z = 4

x + y + z = -1

-3x + 2y - 6z = -7

 


Here's another one for you:

3x - 2y + 5z = 16

2x - y - 3z = 10

4x + 2y + 7z = 12

* Remember to ditch the easiest guy!