Question

There is a protected species of bird living in the desert. There are only 1,234 birds left, and they are decreasing at a rate of 20 percent each year. Which of the following equations would you use to create a sequence modeling this situation?(1 point)
Responses

an=1,234(0.2)n

a subscript n baseline equals 1,234 left parenthesis 0.2 right parenthesis superscript n baseline

an=1,234(0.8)n

a subscript n baseline equals 1,234 left parenthesis 0.8 right parenthesis superscript n baseline

an=1,234(0.2)n−1

a subscript n baseline equals 1,234 left parenthesis 0.2 right parenthesis superscript n minus 1 baseline

an=1,234(0.8)n−1

Answer 1

Answer: a_n = 1,234(0.8)^(n−1)

Explanation: Each year the population is multiplied by 1 − 0.20 = 0.80. For a sequence with a_1 = 1,234, the nth term is a_n = a_1·r^(n−1) = 1,234(0.8)^(n−1). (If you indexed years from 0, you'd use 1,234(0.8)^n.)