Number of Banks - Derivative as a Slope

Spacidy

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Sep 4, 2006
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Directions: answer the question by calculating the slope of the tangent line and the tangent- line equation, as appropriate.

Problem:Number of Banks

Base on data from 1984 to 2000 the number of different banks (not branches of banks) in the US may be modeled by:

B(t) = 2.970(t)^3 - 68.39(t)^2 - 170.9(t) + 18,172


banks, where t is the number of years since 1984.

How quickly was the # of banks decreasing in 2000? What was the estimated # of banks in 2001? (Use a tangent line approximation)

The solution is: 78.42 banks per yr. / 10,016 banks


My problem: I understand the whole tangent line concept - I am actually having the problem with getting the equation simplified before putting it into the tangent formula. (Everytime I try to multiply the B(16+h) to the t^3 it never works out nicely so that I can cancel out like terms)

Any help Would be appreciated VERY much!! I am desperate & frustrated since the easiest part of the problem is what I can't do!!

Thanks!!!
 
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