Question

HELP!

I don't get this:
Solve the system by elimination.

-2x + 2y +3z = 0
-2x - y +z = -3
2x + 3y + 3z = 5

Answer 1

look at this:


-2x + 2y + 3z = 0
2x + 3y + 3z = 5

you can cancel the x out if you add them right?

Answer 2

Right. I got that so far.

Answer 3

so what you'll get is 5y + 6z = 5 right?

Answer 4

right

Answer 5

after you get 5y+6z=5, you find 2 other equations from the ORIGINAL 3 and simplify it down so you get another y + z = ___
.

Answer 6

Thats where I got all mixed up

Answer 7

so now you pick 2 equations from your original 3 like
-2x + 2y +3z = 0
-2x - y +z = -3

and find another y+z=___ to go along with your 5y+6z=5

Answer 8

but they wont cancel eachother out.

Answer 9

you can mutliply one of the equations with -1 to switch up the signs

Answer 10

ohhh ok

Answer 11

I think you get 3y+2z=3? then you just take your 5y+6z=5 and solve for 1 of those variables. then you can practically plug in.

Answer 12

ok Im trying that right now

Answer 13

When I multiply -1 to -2x - y + z = -3, I get 2x +y - z = 3, but you said you got 3y+2z=3?

Answer 14

-2x + 2y +3z = 0
(-2x - y +z = -3)x-1

-2x + 2y +3z = 0
2x +y -z = 3

3y+ 2z = 3

Answer 15

ohh ok. I am so bad at this

Answer 16

haha i was confused too when i started this.

Answer 17

how are you doing on it?

Answer 18

sorry had to step away. still working on it

Answer 19

for y I got y=1, if I did it right

Answer 20

yep i got y=1. now just substitute back into your equation, preferably the y+z, and find z.

Answer 21

ok

Answer 22

so far I have 2 + 4z = 2?

Answer 23

solve for z

Answer 24

4z = 0? so z = 0?

Answer 25

yup! :)

Answer 26

so you have: z=0, y=1, x=_____

Answer 27

yay! ok so now just plug y and z back in to x?

Answer 28

mhm

Answer 29

-2x + 3 = 0 but then what? I subtracted 3 from each side but that didnt work

Answer 30

which equation did you use?

Answer 31

oh wait. I just used 2x + 3 + 0 = 5 and got x = 1
is that right?

Answer 32

pat yourself on the back :)

you can go back and check by plugging in all 3 variables in all 3 equations if you want.

Answer 33

x=1
y=1
z=0

Answer 34

YAY!!! Thank you so much for your help. I think I finally get the hang of it.