Question

solve using matricies
x+2y+3z=7
-x+2y-z=1
-x+y-2z=-2
x= y= z=
ive tried everyway I can think of please help

Answer 1

one way:
Ax=B, so you want A^-1 so that

x = A^-1 B

A =
(1 2 3)
(-1 2 -1)
(-1 1 -2)
B =
(7)
(1)
(-2)

A^-1 = 1/2 *
(3 -7 8)
(1 -1 2)
(-1 3 -4)

Now if you supply the missing value in B, you can do the multiply and get (-1 1 2), the solution.

http://www.wolframalpha.com/input/?i=inverse+{{1,+2,+3},{-1,+2,+-1},{-1,+1,+-2}}+*+{{7},{1},{-2}}

Or, you can do row operations as in Gaussian elimination. There's a handy calculator at

http://www.gregthatcher.com/Mathematics/GaussJordan.aspx