In Multiplication , when bases are same powers are added.
here base = t and powers of t are 1 and 2
hence sum of powers of t =1+2 =3
therefore , t×t²=t³
s²×(-s)= (-s)² × (-s) (because (- s)² = s²)
here base = -s
powers of -s are 2 and 1
sum of powers of -s = 1+2 =3
Apply rule , when bases are same powers are added .
Hope This helps You!!