What are the last three terms of the geometric sequence 800, -400, 200

Answer 1

Assuming the -400 is correct, the common ratio is (-400)/800 = 200/(-400) = -1/2. So the recursive form for the sequence is:

a_n = a_n-1·(-1/2)

So the 4th term (n=4) is:

a₄ = a₃·(-1/2) = 200·(-1/2) = -100

Can you do a₅ and a₆?