If I is the 2x2 identity matrix, show that there is an infinite number of matrices X with integer members such that X*X = I.
(In reply to
Solution by hoodat)
In general:
( a b )
( c a )
where bc = 1  a^2 (therefore one of b or c will be positive, the other negative).
This includes:
( 1 0 )
( x 1 )
where x is any integer.
For example, if a = 8 or 9, the following work (parens/braces not shown):
8 1
63 8
8 3
21 8
8 7
9 8
9 1
80 9
9 2
40 9
9 4
20 9
9 5
16 9
9 8
10 9

Posted by Charlie
on 20070426 09:49:05 