A ball is thrown from an initial height of 2 meters with an initial upward velocity of 20 m/s. The ball's height h (in meters) after t seconds is given by h=2+20t-5t^2. find all values of t for which the ball's height is 12 meters. Round your answers to the nearest tenth of a second.
2+20t-5t^2=12
5t^2-20t+10=0
t^2-4t+2=0 complete the square
t^2-4t=-2
t^2-4t+4=2
(t-2)^2=2
t-2=±\(\sqrt{2}\)
t=2±\(\sqrt{2}\)
t≈(0.586, 3.41)