+385 The equation $y = -16t^2 + 80t$ describes the height (in feet) of a projectile launched from the ground at 80 feet per second. At what $t$ will the projectile reach 36 feet in height for the first time? Express your answer as a decimal rounded to the nearest tenth.
+37146 y = -16t^2 +80 t describes the height.....soooooo
height = 36 ft
36 = -16 t^2 +80t
-16t^2+80t -36 =0 Now use the Quadratic Formula to determine the values of t.....there will be TWO....one (the smaller) will be on the way up and the other will be t for the way down.....obviously you want the smaller one....
\(t = {-b \pm \sqrt{b^2-4ac} \over 2a}\) a = -16 b = 80 c = -36 You should be able to do this now....or you are in the wrong class for your abilities so far
