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?

Question

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?

s · Answer

For a do you take a derivative and then plug in 3 and 4 and find the difference or what ?

anonymous · Answer

a) Avg =  [ f (4) - f(3) ] / ( 4 -3)  
          =  f (4) - f(3)

s · Answer

MMmm ok.. so just a difference with no derivative. Ok thanks!

What about b?

anonymous · Answer

b) instant rate = f' (3)

s · Answer

Ok got it! Thank you!

anonymous · Answer

Thanks for helping me to make it so simple ;)

s · Answer

No problem.. hehe =D