# Homework Help: Simple differentiation

1. Oct 27, 2015

### PhysicsBoyMan

1. The problem statement, all variables and given/known data
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2. Relevant equations
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3. The attempt at a solution
So I wanted to differentiate B(t) by saying

B(t) = P(t)(1.05)20-t ln(1.05)

Apparently this is the wrong answer.

I'm supposed to change my function B(t) into this new form. From there I understand how they differentiated using the quotient rule. I can even understand how they got the new B(t) formula by splitting (1.05)20 from (1.05)-t, then changing that to 1/(1.05)t and multiplying by P(t).
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What I don't understand is why my original attempt is wrong. Why is the new format necessary before we differentiate? It is because I have a negative exponent? Is it because I have two exponents?

Thanks for the help

Last edited by a moderator: May 7, 2017
2. Oct 27, 2015

### Staff: Mentor

B(t) is defined as a product, but it doesn't seem that you used the product rule.

Last edited by a moderator: May 7, 2017