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?

Guest Jan 8, 2019

edited by
Guest
Jan 8, 2019

#1**+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

ElectricPavlov Jan 8, 2019

#2**+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

CPhill Jan 9, 2019