A boy is launching a toy rocket he got for his birthday from the top of an 80 ft building. The function representing the height is f(0) = -16x? +64x + 80 where x represents time in seconds.
How many seconds did it take the rocket to reach it's maximum height?
A
144 sec
B)
2 sec
Eliminate
1.5 sec
D)
128 sec

2 seconds, assuming the "?" in the equation is supposed to be ^2 (the exponent of 2):  f(h) = -16x^2 +64x + 80

Step-by-step explanation:

You can either graph the functuion or take the first derivative to find the maximum height.  The first derivative will give us the slope for a values of x.  The slope at the top height of the rocket is zero, since it has stopped and is starting it's way back down.

First Derivative:

f(x) = -16x^2 +64x + 80

f'(x) = -32x + 64

Set this equal to zero and solve for x

0 = -32x + 64

x = 2 seconds.

Use 2 seconds in the original equation to find the height at 2 seconds.

f(2) = -16x^2 +64x + 80

f(2) = -16(2)^2 +64*(2) + 80

f(2) = 144 feet

Graph:

A graph is attached.  You can locate the maximum at (2,144)

well what you have to do is divide 84 by 6 so theanswer

step-by-step explanation:

84 divided by 6 = 14

and that lightbulb changing party must be freaking lit!