Question 5
The graph (not drawn to scale) of $y=ax^2+bx+c$ with the maximum point at $x=-1$ is shown below. Which of the following must be true?
(I) $a-b+c\gt 0$; (II) $a+b-c\gt 0$; (III) $abc\gt 0$; (IV) $abc\lt 0$.
(I) $a-b+c\gt 0$; (II) $a+b-c\gt 0$; (III) $abc\gt 0$; (IV) $abc\lt 0$.