SOLUTION: A ball is thrown from an initial height of 2 menters with an upward velocity of 13 m/s. The balls height “h” (in meters) after “t” seconds is given by the following. H=2

The fact that the ball reaches the height of 7 meters, means, according to the condition, that


    H = 7,  i.e.  2 + 13t - 5t^2 = 7.


Write it as a quadratic equation in the standard form


    -5t^2 + 13t - 5 = 0;


change the sign everywhere for your convenience


    5t^2 - 13t + 5 = 0


and apply the quadratic formula


     =  = .


The roots are   =  = 0.47 seconds  and   =  = 2.13 seconds .    ANSWER