Answer:
C. 9
Step-by-step explanation:
y = -4x^2 + 2kx
subtitute 3:
y = -4(9)^2 + 2k(9)
y = -4(81) + 18k
let y = 0
=> 0 = -324 + 18k
=> k = 324/18 = 9
this is my calculations hope it helps
Using exponential function concepts, it is found that it represents a decay of 0.9%.
<h3>What is an exponential function?</h3>
A decaying exponential function is <em>modeled </em>by:

In which:
- A(0) is the initial value.
- r is the decay rate, as a decimal.
In this problem, the function is:

Hence:


Thus, it represents a decay of 0.9%.
You can learn more about exponential function concepts at brainly.com/question/25537936
Using a system of equations, it is found that the correct option is:
A) 1389x+1660y=787x+1121y.
<h3>What is a system of equations?</h3>
A system of equations is when two or more variables are related, and equations are built to find the values of each variable.
In this problem, considering the amounts in each olympics(1389 men and 787 women participated on the 19th, 1660 men and 1121 women in the 22th), the system is:
A) 1389x+1660y=787x+1121y.
More can be learned about a system of equations at brainly.com/question/24342899
Well each piece of the whole is what made the whole... so in that case each piece is little 1/4's of the whole....
I would say Jupiter but i may be wrong