Product Rule Derivative Problem

Burjam
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Homework Statement



Use the product rule to differentiate the function:

h(t) = √t(1-t2)

Homework Equations



d/dx[f(x)g(x)] = f(x)g'(x) + g(x)f'(x)

The Attempt at a Solution



(see attachment image)

I checked the back of the textbook and my solution was wrong. The textbook says the answer is (1 - 5t2)/(2√t). What did I do wrong? How do you get this answer?
 

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Between lines 3 and 4 of your work you incorrectly simplified the first term like this:
t^{\frac{1}{2}}(-2t)=-2\sqrt tOtherwise, I agree with your work.
 
Last edited:
Ahh good catch. You would then just do (-2t√t)(2√t) and get -4t2. Add that to 1 - t2 on the numerator and you get (1 - 5t2) / 2√t, the correct answer in the textbook. Thanks.
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
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