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# Volumes of Rotation Watch

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1. Prove that the volume of the solid generated by completely rotating the function y = 6/ (2x + 1) ^1/2
about the x-axis between x=0 and x=4 is 36pi ln 3 units^2

this is what i get?

y^2 = 36/(2x +1)

V= pi [18ln9] - [18ln1]

i dont know where ive gone wrong
2. apart from not putting π outside brackets it looks OK ?
3. (Original post by the bear)
apart from not putting π outside brackets it looks OK ?
the problem is i'm not proving it as 18ln9 -18ln1 x π doesnt = 36π ln3
4. (Original post by Custardcream000)
the problem is i'm not proving it as 18ln9 -18ln1 x π doesnt = 36π ln3

and how to write ln9 another way

*

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Updated: October 9, 2016
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