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If A=[1-1 2-1] , B=[a1b-1] and (A+B)^2=A...

If `A=[1-1 2-1]` , `B=[a1b-1]` and `(A+B)^2=A^2+B^2` , then values of `a` and `b` are `a=4` , `b=1` (b) `a=1` , `b=4` (c) `a=0` , `b=4` (d) `a=2` , `b=4`

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`A=[(1,-1),( 2,-1)]` , `B=[(a,1),(b,-1)]`
and `(A+B)^2=A^2+B^2`
Then
`A+B=[(1,-1),( 2,-1)]+[(a,1),(b,-1)]=[(1+a,0),(2+b,-2)]`
`(A+B)^2=[(1+a,0),(2+b,-2)][(1+a,0),(2+b,-2)]`
`(A+B)^2=[(1+a^2+2a,0),(2+2a+b+ab-4-2b,4)]`
`(A+B)^2=[(a^2+2a+1,0),(2a-b+ab-2,4)]`
...
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