# Volume of solid revolution about $x$-axis limits

Question: Find the volume of solid formed by revolving the region bounded by the given function $$f(x)$$:

$$Y= 3 – x ;$$ about the $$x-$$axis.

How do I find the upper and lower limits of integration ?

• $y=3-x$ is a lineare function, for $x=0$ we get $3$ and for $y=0$ we get also $3$ – Dr. Sonnhard Graubner Feb 20 at 19:08
• Actually, this is the question given. I wrote it as it is. I know how to apply the formula, I just have no idea how to get the limits. – Hala Feb 20 at 19:13
• First of all, use the disk method. The upper limit of integration is going to be $3$ because $3-x=0\implies x=3$. That's the number where the line $3-x$ crosses the x-axis. The lower limit of integration—no idea. It's not entirely clear from your question what it should be. It is poorly formed, I would say. – Michael Rybkin Feb 20 at 19:13
• You need a 3rd element to bound a region when two elements are non-parallel straight lines. A very poorly written question. – Phil H Feb 20 at 20:10