The equation y = -4.9t^2 + 23.8t describes the height (in meters) of a projectile launched from the ground at 23.8 meters per second. In how many seconds will the projectile first reach 18 meters in height?
+1633 y = the height, so we can plug in 18 for y.
−4.9t2+23.8t=18
Then we turn this into a quadratic.
−4.9t2+23.8t−18=0
Then we can use the quadratic formula t=−b±√b2−4ac2a, where a is the coefficient of t^2, b is the coefficient t, and c is the constant.
Plugging in the values we get: approximately 3.92 second
the answer is 3.92004 :)
