Graphing Equations in Three Variables
Example
An inconsistent system of three linear equations
Solve the system:
(1) (2)
(3) |
x 3x
2x |
+ -
+ |
y 2y
2y |
- +
- |
z z
2z |
= 5 = 8
= 7 |
Solution
We can eliminate the variable z from Eqs. (1) and (2) by adding them:
(1) (2) |
x 3x |
+ - |
y 2y |
- + |
z z |
= 5 = 8 |
|
4x |
- |
y |
|
|
= 13 |
To eliminate z from Eqs. (1) and (3), multiply Eq. (1) by 2 and add the resulting
equation to Eq. (3):
-2x 3x |
- + |
2y 2y |
+ - |
2z 2z |
= -10 = 7 |
Eq. (1) multiplied by -2 Eq. (3) |
|
|
|
|
0 |
= -3 |
|
Because the last equation is false, there are two inconsistent equations in the
system. Therefore the solution set is the empty set.
|