Qt A

\((a + b - 1)(a + b - 1) = a^2 + ab - a + ab + b^2 - b - a - b + 1 = a^2 + b^2 + 2ab - 2a - 2b + 1\)

Qt B

\((a + b + 1)(a + b + 1) = a^2 + ab + a + ab + b^2 + b + a + b + 1 = a^2 + b^2 + 2ab + 2a + 2b + 1\)

By comparing both quantities, and removing common terms, we will have

Qt \(A = -(a + b)\)

Qt \(B = a + b\)

We don't know the signs of \(a\) & \(b\), hence we can't decide.

Answer \(D\)