Answer:
D
Step-by-step explanation:
The equation of a parabola in vertex form is
y = a(x - h)² + k
where (h, k) are the coordinates of the vertex and a is a multiplier
To obtain this form use the method of completing the square.
Given
f(x) = - 0.6x² + 4.2x + 240 ← factor out - 0.6 from the first 2 terms
= - 0.6(x² - 7x) + 240
To complete the square
add/ subtract ( half the coefficient of the x- term)² to x² - 7x
f(x) = - 0.6(x² + 2(- 3.5)x + 12.25 - 12.25 ) + 240
= - 0.6 (x - 3.5)² + 7.35 + 240
= - 0.6(x - 3.5)² + 247.35
with vertex = (3.5, 247.35 )
The maximum value is the y- coordinate of the vertex
Then
f(x) = - 0.6(x - 3.5)² + 247.35 has a maximum value of 247.35
