Question 619125
It reaches 9 ft going up and coming back down
{{{ 9 = -16t^2 + 24t + 5 }}}
{{{ -16t^2 + 24t - 4 = 0 }}}
{{{ -4t^2 + 6t - 1 = 0 }}}
Use the quadratic formula
{{{ t = (-b +- sqrt( b^2 - 4*a*c )) / (2*a) }}} 
{{{ t = (-6 +- sqrt( 6^2 - 4*(-4)*(-1) )) / (2*(-4)) }}} 
{{{ t = (-6 +- sqrt( 36 - 16 )) / ( -8 ) }}} 
{{{ t = (-6 +- sqrt( 20 )) / ( -8 ) }}} 
{{{ t = (-3 +- sqrt( 5 )) / ( -4 ) }}} 
I think the answer is (d)