The function y = - X & # 178; + 6x + 9 is in the interval [A.B] (A

The function y = - X & # 178; + 6x + 9 is in the interval [A.B] (A

Analysis: it is obvious that this is a quadratic function, and its axis of symmetry is x = 3. It is obvious that its opening is downward, so it is an increasing function in the interval (- ∞, 3), and because (a)