20 the cost of a hamburger is $2.50. each additional hamburger costs $1.00. sully wrote this explicit rule to explain the sequence of costs: f(n) = 1 + 2.5(n − 1). using this rule, he found the cost of 12 hamburgers to be $28.50. is this number correct? if not, identify sully's error.

Create a question with this scenario you could ask that could be answered only by graphing or using logarithm. david estimated he had about 20 fish in his pond. a year later, there were about 1.5 times as many fish. the year after that, the number of fish increased by a factor of 1.5 again. the number of fish is modeled by f(x)=20(1.5)^x.