Question 749152
{{{ r(t) = 15t^2 + 7t + 830 }}}
Find {{{t}}} when {{{ r(t) = 1412 }}}
{{{ 1412 = 15t^2 + 7t + 830 }}}
{{{ 15t^2 + 7t - 582 = 0 }}}
{{{ t = (-b +- sqrt( b^2 - 4*a*c )) / (2*a) }}} 
{{{ a = 15 }}}
{{{ b = 7 }}}
{{{ c = -582 }}}
{{{ t = (-7 +- sqrt( 7^2 - 4*15*(-582) )) / (2*15) }}} 
{{{ t = (-7 +- sqrt( 49 + 34920 )) / 30 }}} 
{{{ t = (-7 +- sqrt( 34969 )) / 30 }}} 
{{{ t = ( -7 + 187 ) 30 }}} ( can't use the negative square root )
{{{ t = 180/30 }}}
{{{ t = 6 }}}
1998 + 6 = 2004