Answer:
y = 1/3(7)^x.
Step-by-step explanation:
Note that the y values increase by a factor 7:
1/21 = 1/147 * 7, 1/3 = 1/21 * 7, and so on.
So the rule is:
y = 1/3(7)^x.
Check:
When x = 0, y = 1/3 * (7)^0 = 1/3
When x = 2 , y = 1/3(7)^2 = 49/3.
When x = -2 , y = 1/3(7)^-2 = 1/3 * 1/7^2 = 1/147.
