Hello there. To solve this question, we need to remember some properties about quadratic functions and its key features.
Let f(x) = ax² + bx + c, for a not equal to zero.
The main key feature we can see at first glance is the leading coefficient a.
If a < 0, the parabola (the graph of the function) will have its concavity facing down.
If a > 0, the parabola will have its concavity facing up.
It also means the function will have either a maximum or a minimum point on its vertex, respectively.
Another key feature of the function is the y-intercept, i. e. the point in which the x-coordinate is equal to zero, is (0, c).
The x-intercepts of the graph (in plural), are the roots of the function.
If b² - 4ac > 0, we'll have two distinct real roots.
If b² - 4ac = 0, we'll have two equal real roots.
If b² - 4ac < 0, we'll have two conjugate complex roots (not real roots)
This b² - 4ac is the discriminant of the function.
The roots can be found by the formula:
x = (-b +- sqrt(b² - 4ac))/2a
The vertex of the graph can be found on the coordinates (xv, yv), in which xv is calculated by the arithmetic mean of the roots
xv = ((-b + sqrt(b²-4ac))/2a + (-b-sqrt(b²-4ac))/2a)/2 = -b/2a
The yv coordinate can be found by plugging in xv in the function
yv = a(-b/2a)² + b(-b/2a) + c, which will be equal to -(b²-4ac)/4a.