Question

Solve the following system of equations.

x + 3y + 2z = –16
2x – y + 2z = –15
2x – 2y – z = 1

ANSWERS :

(4, 4, –1)
(–3, –1, –5)
(–3, 5, –2)
(2, –4, –3)

Answer 1

y + 3z = -16

its (-3,-1,-5)

Answer 2

Instead of solving the system, you can choose the right answer quickly by adding up the three equations to get
5x+3z=30

and then substitute each of the four answers in the above equation to find out if it works.
(4, 4, –1) : 5*4-3*1=17 no!
(–3, –1, –5) : 5*(-3)-5*3=-30 yes or maybe
(–3, 5, –2) : 5*(-3)-5*2=-25 no!
(2, –4, –3) : 5*2-3*3=1 no!
So there is only one good answer, the second one.
If you find more than one good answer, you'd have to substitute in each equation separately.

Answer 3

THANKS (: