Answer:
f(x) = -(x + 8)(x -14)
= -(x2 - 112 - 6x)
= -x2 + 6x + 112 --- (1)
We know the graph of an equation y = ax2 + bx + c where a ≠ 0 is a parabola. The parabola opens upwards if a > 0 and opens downwards if a < 0. The vertex of the parabola is the point where the axis and parabola intersect. Its x coordinate x = -b/2a and its y coordinate is found out by substituting x = -b/2a in the parabola equation.
The parabola given in the problem statement has a negative coefficient of x2 and hence it is a parabola which opens downwards. Also for the equation
a = -1, b = 6 and c = 112. Therefor the x-coordinate of the vertex is
x = -b/2a
= -(6)/[2(-1)]
= 3
Substituting the value of x = 3 in equation (1) we get,
Now y = -(3)2 + 6(3) + 112
= -9 + 18 + 112 = 121
So the vertex point coordinates are (3, 121) and the y value is 121.
The graph below verifies the vertex point.
vertex of the graph
What is the y-value of the vertex of the function f(x) = -(x + 8)(x - 14)?
Summary:
The y-value of the vertex of the function f(x) = -(x + 8)(x - 14) is 121.