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After an advertising campaign, the sales of a product often increase and then decrease. Suppose that t days after the end of the advertising the daily sales are, f(t) = - 6t^2 + 64t + 105 units. a) What is the average rate of growth in sales during the fourth day that is from time t = 3 to t = 4. b) In what instantaneous rate are the sales changing when t=3?
For a do you take a derivative and then plug in 3 and 4 and find the difference or what ?
a) Avg = [ f (4) - f(3) ] / ( 4 -3) = f (4) - f(3)
MMmm ok.. so just a difference with no derivative. Ok thanks! What about b?
b) instant rate = f' (3)
Thanks for helping me to make it so simple ;)