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## yrivers36 3 years ago Please help me with this system. I'm not getting the y or z. -x+2y+z=2 3x+y+z=12 x-y-2z=-1

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1. satellite73

(3,2,1)

2. yrivers36

Can u explain it to me please?

3. satellite73

are you supposed to use elimation?

4. yrivers36

Either elimination or substitution

5. satellite73

ok we can eleminate z first

6. selenamalter

satellite, i wasnt done, i still needed helpp :/

7. satellite73

\[-x+2y+z=2\] \[ 3x+y+z=12\]

8. satellite73

subtract and get \[-4x+y=-10\] as one equation with no z in it

9. satellite73

now \[3x+y+z=12\] \[ x-y-2z=-1\] multiply first equation by 2 get \[6x+2y+2z=24\] \[x-y-2z=-1\] add and get \[7x+y=23\]

10. satellite73

now we have \[-4x+y=-10\] and \[7x+y=23\] so solve

11. satellite73

subtact second one from first and get \[-11x=-33\] making \[x=3\] now substitute back to find y, and then z

12. yrivers36

Where did the y go in the -4x+y=-10 and 7x+y=23

13. satellite73

i subtracted the second equation from the first

14. yrivers36

oh you multiplied by -1

15. satellite73

or if you prefer, multiply the second by -1 and then add,

16. satellite73

yes exactly it is the same thing

17. yrivers36

ok I got it finally thank you so much for your help

18. satellite73

\[-4x+y=-10\] \[-7x-y=-23\] \[-11x=-33\] etc yw

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