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The function y=-16t^2+8t represents the height y (in feet) of a grasshopper jumping straight up from the ground t seconds after the start of the jump. After how many seconds is the grasshopper 1 foot off the ground?

 Jan 8, 2019
edited by Guest  Jan 8, 2019
 #1
avatar+17332 
+1

When y = 0 the paintbrush hits the ground.

 

0=25-16t^2       solve for t

25=16t^2

25/16 = t^2

t = 5/4 sec      (the other solution for t^2)   -5/4 sec is invalid for a time

 Jan 8, 2019
 #2
avatar+98154 
+1

The function y=-16t^2+8t represents the height y (in feet) of a grasshopper jumping straight up from the ground t seconds after the start of the jump. After how many seconds is the grasshopper 1 foot off the ground?

 

We need to solve this

 

-16t^2+ 8t  =  1      subtract 1 from both sides

 

-16t^2 + 8t - 1  = 0           multiply through by - 1

 

16t^2 - 8t + 1 =  0           factor

 

(4t - 1) (4t - 1) = 0

 

(4t - 1)^2 =  0           take the square root

 

4t - 1 = 0       add 1 to both sides

 

4t  = 1           divide both sides by 4

 

t =  1/4   seconds

 

 

 

cool cool cool

 Jan 9, 2019

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