Respuesta :

Chelboy

Answer:a4=-42

Step-by-step explanation:

a1=0

an=2(a(n-1)-3)

a4=2(a(4-1)-3)

a4=2(a3-3)

a3=2(a(3-1)-3)

a3=2(a2-3)

a2=2(a(2-1)-3)

a2=2(a1-3) but a1=0

a2=2(0-3)

a2=2(-3)

a2=-6

a3=2(a2-3)

a3=2(-6-3)

a3=2(-9)

a3=-18

a4=2(a3-3)

a4=2(-18-3)

a4=2(-21)

a4=-42