X+y-2z=-9
2x-y+8z=99
x-2y+5z=23
give the solution with z arbitrary

  (x, y, z) = (-4, 29, 17)

Step-by-step explanation:

These three equations have a unique solution. If you want "z arbitrary", you need to write a system of two equations with three variables (or, equivalently, a set of dependent equations).

It is convenient to let a graphing calculator, scientific calculator, or web site solve these.

You can reduce the system to two equations in y and z by ...

  subtracting the last equation from the first:

     3y -7z = -32

  subtracting twice the last equation from the second:

     3y -2z = 53

Subtracting the first of these from the second, you get ...

  5z = 85

  z = 17

The remaining variable values fall out:

  y = (53+2z)/3 = 87/3 = 29

  x = -9 +2z -y = -9 +2(17) -29 = -4

These equations have the solution (x, y, z) = (-4, 29, 17).

the image of (6, 9) under a dilation is (4, 6). the scale factor is

the answer is d

step-by-step explanation: