abc
2abc
3abc
4abc
ac
b d
(b - a) (d - c)
(b + a) (a + c)
± 3
± 9
± 6
± 7
6
9
7
-9
1, 9
-1, 9
-1, -9
1, -9
1
2
4
3
and AB = I, then x =
-1
0
3I
5I
-5I
-3I
A 3×3 matrix, whose elements are aij = i+j, is
