Question

Algebra II, please help!
Triple equation system--v
2x + y - z = 7
-x - 2y + 4z = -15
x + 2y - 5z = 17
Which ordered triple is solution of this system?
a. (2,6,5)
b. (1,3,2)
c. (2,5,2)
d. (3,1,0)

Answer 1

I know how to do this because I am actually in Algebra II as well. So do you know what the first step is to solving it?

Answer 2

not really :/ can u walk me thru it ?

Answer 3

Yes, I will be happy too. Okay so first thin first. You want to plug in the #'s. For example:
2*2 + 6 - 5 = 7.
-2 - 2*6 + 4*5 = -15
2 + 2*6 - 5*5 = 17
So you will see if they actually = 7, -15, and 17. And if that doesn't work then plug in the next set and see if that matches.

Answer 4

that works, but if they don't give you the answers you are screwed.

Answer 5

oftentimes to prevent this the question asks you for x+y+z...

Answer 6

you can eliminate 2 variables with a simple look at the last two equations:
-x - 2y + 4z = -15 (2)
x + 2y - 5z = 17 (3)
simply add the two
0+0-z=2

Answer 7

simply solve for z, and you have eliminated a variable.

Answer 8

you can always add together two equations. if one equation has the same constant positive in the one and negative in the other, it is "eliminated":

example:
´´´´´´´´
a + 2 b = 9
-a + b = 2
----------
3 b = 11

variable "a" was "eliminated" by adding the example equations. the same is possible in your problem, see above posts.

Answer 9

But the way they want you to do is do it the way I put up above. Because you will get the right answer if you follow the steps and it is less complicated.

Answer 10

No, the way they WANT you to do it is solve the system.

Answer 11

Exactly.I am prettysure I know what Iam doing. i am taking algebra II