Question 402335
start by factoring out {{{t^2}}}
{{{t^2(t^2-3t-40)=0}}} factor further
{{{t^2(t-8)(t+5)=0}}} set each part equal to zero and solve for t
{{{t^2=0}}} 
{{{t=0}}}
{{{t-8=0}}}
{{{t=8}}}
{{{t+5=0}}}
{{{t=-5}}}
So the answers are t=0, or t=8 or t=-5.