Gary L.

asked • 07/25/17

Is it possible to solve a matrix by only having one row and one column of data?

Is it possible to solve a matrix by only having one row and one column of data? 
 
For example: 
                                                    Consequences
 
                            Insignificant   Minor  Moderate  Major   Catastrophic
                                     1             2          3            4             5
Likelihood            -----------------------------------------------------------        
Almost Certain  5|                                     15
Likely               4|                                     12
Possible            3|          3             6           9          12           15
Unlikely            2|                                      6
Rare                 1|                                      3
 
Can the rest of this be completed by using an equation(s)?
 
 

Gary L.

Sorry that the formatting got messed up when posted. All values are in column 3 and row 3. Thanks.
Report

07/25/17

2 Answers By Expert Tutors

By:

Arturo O. answered • 07/25/17

Tutor
5.0 (66)

Experienced Physics Teacher for Physics Tutoring

Arturo O.

So the short answer is no.  To solve the matrix, you need to be able to invert it, which you cannot do because its determinant is zero.
Report

07/25/17

Andy C. answered • 07/25/17

Tutor
4.9 (27)

Math/Physics Tutor

Gary L.

Hi Andy,
 
Thanks for the response.
 
So if you had the diagonals, would it be solvable?
 
Thanks,
Gary
Report

07/25/17

Arturo O.

When in diagonal form, it is also necessary that no element on the diagonal be zero, because that would make the determinant zero, and hence you would not have a solution.
Report

07/25/17

Andy C.

When reduced using matrix operations, the pivot elements cannot be zero.
That is row1,column1
           row2,column2
           row3,column3,
          etc.
 
If none of the pivot elements are zero, then there will be a unique 
solution.
 
Otherwise, one of two things will happen.
 
If two of the equations are algebraically the same,
then you don't have enough equations. You will
have a free variable, or one degree of freedom.
There are INFINITELY many solutions.
In that case, you select the free variable and write
the other equations in terms of the free variable.
 
The other possibility is illustrated by this problem
in that two equations in the system produce
contradiction results in which case, there is no
solution to the system.
 
Here is an example of the second scenario.
 
  2X + 3Y = 10
  4x + 6Y = 20
 
clearly these two equations are the same, as the second is simply double the first.
The row operation -2*row1 + row2 will kill the second equation, so there is only
one equation left with two unknowns.
Selecting X as the free variable, the solution to the system is the line 3Y = 10 - 2X
   or y = -2/3X + 10/3
 
Every time a pivot is zero, you get another free variable.
So for example, in a system of 10 equations with 10 unknowns,
if 2 of the pivots are zero, then you will have 2 free variables,
or 2 degrees of freedom.
 
Report

07/25/17

Gary L.

Thank you both for your responses. I appreciate it very much.
 
I realize now that my example wasn't the best one to illustrate. So what about this one?
 
1   |    22.44 | 22.28 | 22.12
0   |    22.24 | 22.08 | 21.92
-1  |    22.05 | 21.89 | 21.73
     -------------------------------
          -0.001     0      0.001
 
Is it possible to extend this 3x3 matrix to a 4x4 matrix by using a few equations?
 
Thanks again to both of you, Andy and Arturo.
Report

07/25/17

Still looking for help? Get the right answer, fast.

Ask a question for free

Get a free answer to a quick problem.
Most questions answered within 4 hours.

OR

Find an Online Tutor Now

Choose an expert and meet online. No packages or subscriptions, pay only for the time you need.