Answer:
(a) 157 million
(b) 2018
Step-by-step explanation:
(a) Since x=11 corresponds to the year 2011, we presume that x is 'years after 2000', and that for 2013, we need to use x=13.
f(13) = -879 +404·ln(13) ≈ 157.24
About 157 million phones were sold in 2013.
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(b) To find the year that sales exceeded 275 million, we solve ...
f(x) = 275
-879 +404·ln(x) = 275
404·ln(x) = 1154
ln(x) = 1154/404
x = e^(1154/404) ≈ 17.399
Sales will first exceed 275 million in 2017. The first full year in which sales are over 275 million is 2018.
