Answer:
B
Step-by-step explanation:
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Answer. First option: t > 6.25
Solution:
Height (in feet): h=-16t^2+729
For which interval of time is h less than 104 feet above the ground?
h < 104
Replacing h for -16t^2+729
-16t^2+729 < 104
Solving for h: Subtracting 729 both sides of the inequality:
-16t^2+729-729 < 104-729
-16t^2 < -625
Multiplying the inequality by -1:
(-1)(-16t^2 < -625)
16t^2 > 625
Dividing both sides of the inequality by 16:
16t^2/16 > 625/16
t^2 > 39.0625
Replacing t^2 by [ Absolute value (t) ]^2:
[ Absolute value (t) ]^2 > 39.0625
Square root both sides of the inequality:
sqrt { [ Absolute value (t) ]^2 } > sqrt (39.0625)
Absolute value (t) > 6.25
t < -6.25 or t > 6.25, but t can not be negative, then the solution is:
t > 6.25
Answer:
The tip of the man shadow moves at the rate of 
Step-by-step explanation:
Let's draw a figure that describes the given situation.
Let "x" be the distance between the man and the pole and "y" be distance between the pole and man's shadows tip point.
Here it forms two similar triangles.
Let's find the distance "y" using proportion.
From the figure, we can form a proportion.

Cross multiplying, we get
15(y -x) = 6y
15y - 15x = 6y
15y - 6y = 15x
9y = 15x
y = 
We need to find rate of change of the shadow. So we need to differentiate y with respect to the time (t).
----(1)
We are given
. Plug in the equation (1), we get

Here the distance between the man and the pole 45 ft does not need because we asked to find the how fast the shadow of the man moves.
B - 8x
To find this, combine like terms.
8x - 2x is 6x, then add the two x's on the side to bring it back to 8x.
Hope this helps!