Integration Problem

[book]

Hello there,

I did this question, but I'm getting the wrong answer and I don't know where I am making the mistake. I'm also uploading my working out. Could anyone help? Thanks

 

[Deleted member 4993]

Hello there,

I did this question, but I'm getting the wrong answer and I don't know where I am making the mistake. I'm also uploading my working out. Could anyone help? Thanks

View attachment 33961

Apparently you are using the washer-method. The thickness of the washer (disc) is dy and NOT dx. Thus you started the problem incorrectly. The volume of the thin disc is:

dV = π * x² * dy

Try again......