Question 371206
Since you posted this problem under "Matrices and Determinants" I assume you know what they are.<br>
The fast way to determine whether or not there is a unique solution is to find the value of the following determinant:
<pre>
|   7  -2  |
| -28   8  |
</pre>
The value of this determinant is 7*8 - (-28)*(-2) = 56 - 56 = 0. Since this determinant is zero there is no unique solution. (If this determinant had worked out to be non-zero, then there would be a unique solution.)