the objects are in the same position at the same time. Suppose the trajectories of two particles are given by the vector functions

$r_1(t)=($:$t^2,10t-24,t^2$:$),r_2(t)=($:$7t-6,t^2,13t-42$:$)$

for $t0.$ Find the values of $t$ at which the particles collide. $($Enter your answers as a comma$-$separated list. If an answer does not exist, enter DNE.$)$

$t=$