Cho hàm số \(y =  - {x^2} + 2x +...

Câu hỏi: Cho hàm số \(y =  - {x^2} + 2x + 3.\)

A \({\rm{b)}}\,\,m <  - \frac{1}{2}\,\,;\,\,m \ne  - 1\)

B \({\rm{b)}}\,\,m >  - \frac{1}{2}\,\,\).

C \({\rm{b)}}\,\,m < \frac{1}{2}\,\,;\,\,m \ne  - 1\)

D \({\rm{b)}}\,\,m > \frac{1}{2}\,\,;\,\,m \ne 1\)