Respuesta :

Fist : 3

then

second : x (-3) = - 9

third : x (-3) = 27

x (-3) = - 81

the 15 term ?

first one = 3 x (-3)⁰

second one = 3 x (-3)¹

third one = 3 x (-3)²

so n one = 3 x (-3)ⁿ⁻¹

then the 15th one = 3 x (-3)¹⁴