Question 733322
{{{ h(t) =-15t^2+105t+10 }}}
{{{ h(t) = 190 }}} ft
{{{ 190 =-15t^2+105t+10 }}}
{{{ -15t^2 + 105t - 180 = 0 }}}
{{{ -t^2 + 7t - 12 = 0 }}}
Use quadratic formula
{{{ t = ( -b +- sqrt( b^2 - 4*a*c )) / (2*a) }}} 
{{{ a = -1 }}}
{{{ b = 7 }}}
{{{ c = -12 }}}
{{{ t = ( -7 +- sqrt( 7^2 - 4*(-1)*(-12) )) / (2*(-1)) }}} 
{{{ t = ( -7 +- sqrt( 49 - 48 )) / (-2) }}} 
{{{ t = ( -7 +- sqrt( 1 )) / (-2) }}} 
{{{ t = ( -7 + 1 ) / (-2) }}} 
{{{ t = 3 }}}
also
{{{ t = ( -7 - 1 ) / (-2) }}} 
{{{ t = 4 }}}
There are 2 times when it is 190 ft above ground, 3 sec and 4 sec
check:
{{{ graph( 400, 400, -2, 10, -200, 20, -15*x^2 + 105x - 180 ) }}}