Solve the following system of equations for all three variables.
-7x+y+z=
−7x+y+z=
\,\,-9
−9
-7x+5y-9z=
−7x+5y−9z=
\,\,-3
−3
7x-6y+4z=
7x−6y+4z=
\,\,-6
−6

(x,y,z) -> (2,4,1)

Step-by-step explanation:

-7x + y + z = -9

-7x + 5y - 9z = -3

7x - 6y + 4z = -6

Pick two pairs:

-7x + 5y - 9z = -3

7x - 6y + 4z = -6

and

-7x + y + z = -9

-7x + 5y - 9z = -3

Eliminate the same variable from each system:

-7x + 5y - 9z = -3

7x - 6y + 4z = -6

+ 5y - 9z = -3

- 6y + 4z = -6

-1y - 5z = - 9

-7x + y + z = -9

-7x + 5y - 9z = -3

-7x + y + z = -9

7x - 5y + 9z = 3

-4y - 10z = -6

Solve the system of the two new equations:

-1y - 5z = - 9           ->      -4 ( -1y - 5z = - 9)     ->   4y + 20z = 36  

-4y - 10z = -6          ->           -4y - 10z = -6      ->   -4y - 10z = -6

10z = 30

Thus, z = 3

-4y - 10z = -6

-4y - 10(3) = -6

-4y - 30 = -6

-4y = 24

Thus, y = -6

Substitute into one of the original equations:

-7x + y + z = -9

-7x + (-6) + (3) = -9

7x + -3  = -9

7x  = -6

x =

the answer is d

the answer is in the first quadrant, which make the y-int positive.

since the dots are going down, therefore the correlation is negative

i hope it is right.