Will mark brainiest! The first question since it got cut off is : (A) is the sequence arithmetic, geometric, or neither? How do you know?

Geometric, 81, 3

Step-by-step explanation:

A geometric sequence is defined as one that continues with multiplication.

We can tell that the sequence proceeds by multiplying 1/3.

a2 is 81 because it is the second term given in the sequence.

a5 is 3 because it equals a4 *1/3, which is 9*1/3 which is 3

I hope this helps! :)

step-by-step explanation:

the original amount doesn't ''re just looking for the time it takes for 1/2 of the substance to we have

(1/2) =)     take the ln   of both sides

ln (1/2)   = )   and we can write

ln(1/2) = ) lne     and lne   = 1     so we have

ln(1/2) = -.1092t     divide both sides by -.1092

t = ln(1/2)/-.1092 = about 6.347 days = about 6.3 days (rounded)