Answer:
D. 
Step-by-step explanation:
The period of the functions
is 
The period of the function
is ALWAYS 
In your case, you have function
and this function has the period

You need to find the function that will have the period that is half of
so

So, correct choice is

Please see the pic, I'd solved in it.
Answer:
Step-by-step explanation:
To solve this problem you need the function
h(t) = -16t2 + v0t + h0
where t = time
v0 is the initial velocity, which in our case is 0
h0 = initial height, which in our case is 256
h(t) = 0 since we want to know when the ball will hit the ground.
0 = -16 t2 + 256
And we can solve for t
If we rearrange the terms we see that this is a difference of 2 squares
0 = 256 - 16t2
0 = (16-4t)(16+4t)
Setting each factor = 0
16-4t=0 16+4t=4
t = 4 t = -4
The second solution is discarded as time cannot be negative.
So the ball will hit the ground in 4 seconds.
X - the number of pencils
y - the number of pens
She has twice as many pencils as she has pens.

Tom borrows a pen, so she has y-1 pens. Now she has ten less pens than pencils.

Set 2y and y+9 equal to each other:
She has 9 pens.