Question

I don’t know how to do these..
8.

Solve the system by elimination.
{-2x + 2y + 3z = 0
{-2x – y + z = -3
{2x + 3y + 3z = 5

9. Solve the system by substitution.

{-x – y – z = -8
{-4 + 4y + 5z = 7
{2x + 2z = 4

Answer 1

add 1st and 3rd eqns to eliminate x
... 5y + 6z = 5 ... (A)

add 2nd and 3rd eqns to eliminate x
... 2y + 4z = 2 ... (B)

multiply B by -3/2 and add to A to elim z
... 2y = 2

solve for y, then substitute back to find x and z


solve 3rd eqn for x ... x = 2 - z

substitute for x in the 1st and 2nd eqns
... y = 6 ... (A)
... 4y + 9z = 15 ... (B)

substitute the value of y from A into B
... 4(6) + 9z = 15

solve for z, then substitute back to find x