Question

Which table shows exponential decay?

A 2-column table has 4 rows. The first column is labeled x with entries 1, 2, 3, 4. The second column is labeled y with entries 16, 8, 4, 2.
A 2-column table has 4 rows. The first column is labeled x with entries 1, 2, 3, 4. The second column is labeled y with entries 16, 128, 8, 4.
A 2-column table has 4 rows. The first column is labeled x with entries 1, 2, 3, 4. The second column is labeled y with entries 16, 12, 9, 7.
A 2-column table has 4 rows. The first column is labeled x with entries 1, 2, 3, 4. The second column is labeled y with entries 16, 8, 3, 1.

Answer 1

Only the first table (y = 16, 8, 4, 2) shows exponential decay. Each term is half the previous one (ratio = 1/2 < 1), so y = 16*(1/2)^(x-1) (equivalently y = 32*(1/2)^x).