Find Length of Arc for x = 3y^(4/3) - 3/32y^(2/3)

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Homework Statement



find the length of the arc


x = 3y^ (4/3) - 3/32y^(2/3) and y lies between 0 and 216


Homework Equations



l = integral sqrt (1 + (dy / dx )^2)

The Attempt at a Solution




after integration i got this y + 3/16y ^(-4/3) / (-4/3)

i have to apply 0 and 216 is that correct i get a ridiculous answer
 
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You can easily check if your answer is correct or not by differentiating the primitive you've found with respect to y. If it is the correct one it should equal the integrand after differentiation. In your case this is not true, so you didn't integrate correctly.
 
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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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