Question 763740
{{{-16t^2 + 64t + 160=40}}}
{{{-16t^2 + 64t + 120=0}}} divide by {{{-8}}}
{{{2t^2 -8t - 15=0}}}
{{{t=(-(-8)+-sqrt(8^2-4*2*(-15)))/(2*2)}}}
{{{t[1]=(8+sqrt(184))/4=(8+2sqrt(46))/2=(4+sqrt(46))/2=5.391}}}
{{{t[2]=(8-sqrt(184))/4=(8-2sqrt(46))/2=(4-sqrt(46))/2=-1.391<0}}}
{{{t=5.391}}} sec