Answer:
[tex]\large\boxed{{\sf \left \{ {{t_1 = -10} \atop {t_n = -2t_{n-1}}} \right. }}[/tex]
Explanation:
geometric sequence: [tex]\sf a_n = a_{n-1} \ x \ r[/tex] where "r" is common ratio
Find "r" = second term ÷ first term = 20 ÷ -10 = -2
Recursive rule:
[tex]\boxed{\sf t_n = r(t_{n-1})}[/tex]
[tex]\large\boxed{{\sf \left \{ {{t_1 = -10} \atop {t_n = -2t_{n-1}}} \right. }}[/tex]
