Question 436189
Since {{{c < 0}}}, then {{{y(0) < 0}}}, so the entire parabola must be contained within the third and fourth quadrants. Hence, {{{a < 0}}}.


The vertex of the parabola occurs at {{{x = -b/2a}}}. Since b is positive and a is negative, {{{-b/2a}}} will be positive. The vertex has a positive x-coordinate and a negative y-coordinate, so it lies in the fourth quadrant, and choice C is correct.