Answer: -2t(7t-4)
Explanation: We know that perimeter is each side added, so take those two expressions and then them twice.
-10t^2-t + -10t^2-t = -20t^2-2t
and
3t^2+5t + 3t^2+5t= 6t^2+10t
then take those 2 resulting expressions and add them.
-20t^2-2t+6t^2+10t
combine like terms
-14t^2+8t
simplify
-2t(7t-4)
hopefully that’s right i may have made a mistake so just overlook it -just in case