SOLUTION: how can i do this: x-y+z=0 3x-2y+6z=9 -x+y-2z=21

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Question 117577This question is from textbook
: how can i do this:
x-y+z=0
3x-2y+6z=9
-x+y-2z=21
This question is from textbook

Answer by MathLover1(20850)   (Show Source): You can put this solution on YOUR website!
………(1)
……………..(2)
…………..(3)

In order to solve this system for , , and , first you need to eliminate one unknown variable. If you look at (1) and (3) you will see that and have opposite signs and same coefficient which is ; so, we can add these and eliminate and and find out what is.
………(1)

+…………..(3)
------------------------------
……….cancel and

………multiply both sides by
……………………solution #1
Now plug in solution #1 in equation (1) , (2), or (3). I will choose equation (1) and multiply it by , then subtract (2) from (1) to find out what is.
………multiply both sides by ………….(1)
……………..(2)
--------------------------------------------
………………….(1)………. subtract (2) from (1)
-……………..(2)
---------------------------------------------
……

……
……
……
……multiply both sides by

……solution #2
Now choose either one of the three equations, plug in values for and and find out what is.
…………………………….(1)

……
……
……

Check:
……..............(1)
……
……
……

……..............(2)




Check …(3)… by yourself

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