Question

4x + y =3
x + y - z = 9
2x + 2y + z = 0

Answer 1

`[0, 3, -6]`

Explanation:

{4x + y = 3

{x + y - z = 9 ←

{2x + 2y + z = 0 ←

{4x + y = 3

{3x + 3y = 9 >> Combined equation

−¾[4x + y = 3]

{−3x - ¾y = −2¼ >> New Equation

{3x + 3y = 9

_________

2¼y = 6¾

___ ___

2¼ 2¼

`y = 3` [Plug this back into all three equations to get the z-value of −6, and the x-value of 0];
`0 = x`;
`-6 = z`

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