Because 5120 and 1280 are quite large numbers, we can find what is being done in the sequence by looking at 320 and 80, where 320 is being divided by 4. Now that we know that this is process, we can just divide 80 by 4 to get 20, the first missing term, and 20 by 4 to get 5, the second missing term. I hope this helps!