18. Let
What is the entry on the first column of the third
row of A-1 ?
| A. -3 | B. -1 | C. -1/2 | D. 1 | E. 2 |
Solution The answer is C.
To start, let
where the asterisks denote values of no importance
to this problem. Computing the third row of A-1
A we have
That is, since A-1A is the identity
matrix
Next, since b = 0, the first and third equation
imply that c = 1. Finally, a = -1/2.