Which of the following should Mindy use to describe the data?

Question

Mindy is working on her math homework. One problem presents her with the following data and asks her to write an exponential function rule that can describe the data. 

x f(x)

-2 640

-1 160

0 40

1 10

2 2.5

3 0.625

Which of the following should Mindy use to describe the data?

a
b
c
d

Answer 1

The answer is d because if you put 0 into 40(1/4)^x you get 40(1) because any number raised to 0 is 1. if you put in one into 40(1/4)^x you get 40(1/4) which is 10 and if you put in -1 you get 40(1/4)^-1 which equals 40(4) bec and 40(4)=160 since 40 is adding to itself four times. The rest of the values can then be assumed to fit the equations due to it being valid for three of them.