Answer
No, the restaurant food-and-drink sales are not increasing at a steady rate.
Work Step by Step
From 2005 to 2010, sales increased from 474.9 billion dollars to 574.5 billion dollars, for an increase of 99.6 billion dollars.
From 2010 to 2015, sales are estimated to increase from 574.5 billion dollars to 683.6 billion dollars, for an increase of 109.1 billion dollars.
Because of the positive exponent term in the function, sales will increase by a larger amount as x, the number of years since 1970, increases.
