Question 1146642
{{{ h = 3 + 15t - 5t^2 }}}
{{{ 11 = 3 + 15t - 5t^2 }}}
{{{ -5t^2 + 15t - 8 = 0 }}}
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{{{ t = (-b +- sqrt( b^2-4*a*c ))/(2*a) }}} 
{{{ a = -5 }}}
{{{ b = 15 }}}
{{{ c = -8 }}}
{{{ t = (-15 +- sqrt( 15^2 - 4*(-5)*(-8) ))/(2*(-5)) }}} 
{{{ t = (-15 +- sqrt( 225 - 160 ))/( -10 ) }}} 
{{{ t = ( -15 +- sqrt( 65 ) ) / (-10) }}}
{{{ t = ( -15 + 8.06226 ) / (-10) }}}
{{{ t = ( -6.93774 ) / (-10 ) }}}
{{{ t = .69377 }}} sec
and, also:
{{{ t = ( -15 - 8.06226 ) / (-10) }}}
{{{ t = 23.06226 / 10 }}}
{{{ t = 2.3062 }}} sec
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{{{ graph( 400, 400, -2, 6, -2, 15, -5x^2 + 15x + 3 ) }}}
The answers look correct -check my math