Integration (1 Viewer)

[cwag]

proabably one volume comes out negative....what were were you getting?

 

[FDownes]

I've lost my original answer now, since I whited it out and started again (several times...). I think it was something like 254pi/6.

I could really use some help with this...

 

[FDownes]

Ugh... I'll just move on to the next question. Unfortunately, I seem to be stuck on that one too...

Find the derivative of x√(x + 3)

It should be simple, but my answer is missing an x where (according to the answer) there should be one. Can anyone help?

EDIT: Never mind, got it. Was making another silly mistake.

 

[FDownes]

Another;

Find the volume of the solid formed if the curve y = x√(x² - 1) is rotated about the x-axis between x = 1 and x = 2.

The first part of this question required me to figure out the area enclosed between the curve and the x-axis, between the same x values. The result was √3. Is there a shorter method of using this result to find the volume, or do I have to integrate the equation completely using pi y²?

 

[tommykins]

y² is still pretty simple.

y² = (x√(x²-1))² = x²(x²-1) => x^4 - x²

integrate pi etc.

 

[FDownes]

Ah... I just wasn't sure what to do with (x√(x²-1))². Thanks.