Other · Multi-part · ISC · Mathematics · Coordinate Geometry · Forms of a line equation
Problem
Valéria joins a social networking website. After 1 week she has 34 online friends, and after 9 weeks she has 80 online friends.
(1) a** Find the average number of online friends Valéria has made each week from week 1 to week 9.
(2) b** Assuming that her total number of online friends after n weeks forms an arithmetic sequence, find a model which approximates the number of online friends after n weeks.
(3) c Do you think it is a problem that the common difference in your model is not an integer? Explain your answer.
(4) d Use your model to predict how many online friends Valéria will have after 20 weeks.