Question

Solve the following system.
-3x + 2y + z = -6
x + 3y + 2z = 5
4x + 4y + 3z = 13.

I got z= -5, y=4 and x=3.

My teacher told me I did not show my work and she didn't wouldn't take credit for it, even if it was right. Please step out the problems for me and show me what I need to do to get my answer, how to show my work and solve for it. I really need to know this question. SOMEONE please help. I'm desperate.

Answer 1

-3x + 2y + z = - 6 ---->(-2)
x + 3y + 2z = 5
----------------
6x - 4y - 2z = 12 (result of multiplying by -2)
x + 3y + 2z = 5
----------------add
7x - y = 17

what you eliminate in the first 2 equations, you must eliminate in the second 2.

x + 3y + 2z = 5 ---->(3)
4x + 4y + 3z = 13 --->(-2)
--------------
3x + 9y + 6z = 15 (result of multiplying by 3)
-8x - 8y - 6z = - 26 (result of multiplying by -2)
--------------add
-5x + y = - 11

now take your results
7x - y = 17
-5x + y = -11
-------------add
2x = 6
x = 6/2
x = 3

now we sub into an equation that does not have a z in it.
-5x + y = -11
-5(3) + y = -11
-15 + y = -11
y = -11 + 15
y = 4

now sub back into original equation
x + 3y + 2z = 5
3 + 3(4) + 2z = 5
3 + 12 + 2z = 5
2z = 5 - 15
2z = - 10
z = -10/2
z = -5

now we check..
-3x + 2y + z = -6
-3(3) + 2(4) + (-5) = -6
-9 + 8 - 5 = -6
-14 + 8 = -6
-6 = -6 (correct)

x = 3, y = 4, and z = -5

Answer 2

anytime...its not really that hard, just a little time consuming