Derivative of compound interest

In summary, to find the derivative of f(x) = (1/x+1)^x, you can use the formula for the derivative of a^x = ln(a) a^x and the chain rule. By rewriting (1/x+1) as exp(ln(1/x+1)), you can differentiate f(x) as exp((ln(1/x+1))*x). Don't forget the chain rule.
  • #1
lax1113
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Homework Statement


f(x) = (1/x+1)^x, find f'(x)


Homework Equations


derivative of a^x = ln(a) a^x


The Attempt at a Solution


When I differentiate i get ln((1+x)/x)*((1+x)/x)^x... However, this solution does not match what I should be getting. Am i differentiating wrong at some point? or are my notes that claim a^x = lna*a^x wrong...
 
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  • #2
Your formula for a^x assumes a is a constant. The easiest way to handle this one is to use (1/x+1)=exp(ln(1/x+1)) so f(x)=exp((ln(1/x+1))*x). Now just differentiate and don't forget the chain rule.
 
  • #3
duh!


thanks so much dick I can't believe I stared at it for that long and didn't realize that.
 

FAQ: Derivative of compound interest

What is compound interest?

Compound interest is a type of interest that is calculated not only on the initial amount invested, but also on any accumulated interest from previous periods. This means that the interest earned in each period is added to the principal amount, and interest is then calculated on the new total.

How is the derivative of compound interest calculated?

The derivative of compound interest is calculated using the formula dP/dt = P(1+r)^t ln(1+r), where P is the initial principal amount, r is the interest rate, and t is the time period. This formula takes into account the compounding effect of interest over time.

What is the significance of the derivative of compound interest?

The derivative of compound interest is important because it allows us to determine the rate at which the value of an investment is changing over time. This can help us make informed decisions about investments and understand the impact of changing interest rates on the value of our investments.

How does the frequency of compounding affect the derivative of compound interest?

The frequency of compounding does not affect the derivative of compound interest, as long as the interest rate remains constant. This is because the derivative is calculated based on the total interest rate, regardless of how frequently it is compounded.

Can the derivative of compound interest be negative?

Yes, the derivative of compound interest can be negative if the interest rate is negative or if the value of the investment is decreasing over time. This means that the value of the investment is decreasing at a certain rate, rather than increasing as it would with positive compound interest.

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