SOLUTION: If one of you has a moment can you please help. A ball is propelled upward from ground level. After t seconds, its height in feet is a function defined by f(t)=-16t^2 + 96t.

Algebra ->  College  -> Linear Algebra -> SOLUTION: If one of you has a moment can you please help. A ball is propelled upward from ground level. After t seconds, its height in feet is a function defined by f(t)=-16t^2 + 96t.       Log On


   

Question 411661: If one of you has a moment can you please help.
A ball is propelled upward from ground level. After t seconds, its height in feet is a function defined by f(t)=-16t^2 + 96t. After how many seconds will it reach a height of 144 feet?
a. 2 seconds
b. 3 seconds
c. 4 seconds
d. 6 seconds
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
+f%28t%29=-16t%5E2+%2B+96t
144+=+-16t%5E2+%2B+96t
-16t%5E2+%2B+96t+-+144+=+0
-t%5E2+%2B+6t+-+9+=+0
%28-t+%2B+3%29%2A%28t+-+3%29+=+0 (I just figured it out- pretty simple)
t+=+3
The answer is (b)
check answer:
144+=+-16%2A3%5E2+%2B+96%2A3
144+=+-144+%2B+288
144+=+144
OK