If `A=[1 2 2 2 1-2a2b]`
is a matrix satisfying the equation `AA^T=""9I`
,
where `I`
is `3xx3`
identity matrix, then the ordered pair (a,
b) is equal to :
(1) `(2,-1)`
(2) `(-2,""1)`
(3) (2, 1) (4) `(-2,-1)`
A. `(2,-1)`
B. `(-2,1)`
C. `(2,1)`
D. `(-2,-1)`