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?
+36916 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
+128475 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
