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
Change in value = 87 - 42 = 45
percentage change = 45/42 x 100 = 107%
Perimeter (p) = length around a shape.
So any horizontal sides we can add based upon their length in x-values and any vertical sides we can add based upon their length in y-values. The diagonal sides we can find by the distance formula:

So the bottom base goes from x=1 to x=8, then up 1, right 1, and up from y=3 to y=9, then left from x=9 to x=6, down from y=9 to y=6, left from x=6 to x=3.
So far that is: (8-1)+1+1+(9-3)+(9-6)+(9-6)+(6-3)
= 7+2+6+3+3+3 = 24
Now for the diagonal:

P = 24 + 4.47 = 28.47
D) 28.472
Answer:
144
Step-by-step explanation: