Answer:
The vertex of the function is at (–3,–16)
The graph is increasing on the interval x > –3
The graph is positive only on the intervals where x < –7 and where x > 1
Step-by-step explanation:
The roots of this function are the values that make f(x) = 0. As the equation is already factored, we can see that the roots are x1 = 1 and x2 = -7
The x-coordinate of the vertix can be calculated as:
x_v = (x1 + x2)/2 = -6/2 = -3
So the first statement: "The vertex of the function is at (–4,–15)" is wrong.
The y_coordinate of the vertex is:
f(x_v) = (x_v - 1)*(x_v + 7) = (-3 -1) * (-3 +7) = (-4) * (4) = -16
So the second statemente: "The vertex of the function is at (–3,–16)" is correct.
for values of x greater than x_v = -3, the graph increases, as the equation represents a parabola with concavity upwards. So the third statement is correct.
As the roots are 1 and -7 and the concavity is upwards, the parabola have positive values for x<-7 and x>1. So the fourth statement is correct.
For values of x< -4, the parabola can have both positive or negative values (it has positive values for x < -7) so the fifth statement is wrong.
