Question 950715
{{{ s > 1050 }}}
{{{ s = -14t^2 + 280t }}}
----------------------
Set {{{ s = 1050 }}} ft
{{{ 1050 = -14t^2 + 280t }}}
{{{ -14t^2 + 280t - 1050 = 0 }}}
{{{ -7t^2 + 140t - 525 = 0 }}}
{{{ -t^2 + 20t - 75 = 0 }}}
I notice that {{{ 75 = 15*5 }}}, so I
can say:
{{{ ( -t + 15 )*( t - 5 ) = 0 }}}
{{{ -t + 15 = 0 }}}
{{{ t = 15 }}}
and
{{{ t - 5 = 0 }}}
{{{ t = 5 }}}
-------------
{{{ s > 1050 }}} ft for 
{{{ t > 5 }}} sec
{{{ t < 15 }}} sec
---------------
{{{ 5 < t < 15 }}} sec
------------------
Here's the plot:
{{{ graph( 400, 400, -5, 25, -300, 1500, -14x^2 + 280x, 1050 ) }}}