Answer:
-21
Step-by-step explanation:
3,_,_,-1029
r=n-k√an(n should be small in size)
Over ak(k should be small in size)
r=4-1√a4(4 should be small in size)
Over a1(1 should be small in size))
r=3√-1029
Over 3
r=3√-343
r=-7(common difference)
Multiply to the first geometric extreme(given #)
3×-7=-21
-21×-7=147
147×-7=-1029
