Urgent help with integration! (1 Viewer)

[mkv_86]

I've attached two photos, it's a question on volumes integration (2U), and on my second attachment is my working out. Is it correct?
And also when do I use this method of subtracting the volume under the curve from the volume of the cylinder? i.e ∏r^2h

https://dl2.pushbulletusercontent.com/U1kMx7WcrFSALExcpPnyQvkkiB9U7H3J/20180106_174234.jpg

 

[Drongoski]

I think the reqd integral is:

 

[kpad5991]

Can you give me the exercise and number of the question I'll send you a phot of the solutions

 

[ichila101]

Your method is totally correct but you made a simple mistake with 64pi - 64/5pi being equal to 256/5pi not 241/5pi. Other than that, you can use the subtracting from cylinder method as long as the other function (i.e. (x-2)^2) is not above the line y=4

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[HeroWise]

I think the second part is just redundant, try to do it in one step like Drongoski has proposed,