How do you do this question?

Answer:
Solution : Option B, or 9π
Step-by-step explanation:
We are given that y = x, x = 3, and y = 0.
Now assume we have a circle that models the given information. The radius will be x, so to determine the area of that circle we have πx². And knowing that x = 3 and y = 0, we have the following integral:
[tex]\int _0^3[/tex]
So our set up for solving this problem, would be such:
[tex]\int _0^3x^2\pi \:[/tex]
By solving this integral we receive our solution:
[tex]\int _0^3x^2\pi dx,\\\mathrm{Take\:the\:constant\:out}:\quad \int a\cdot f\left(x\right)dx=a\cdot \int f\left(x\right)dx\\=> \pi \cdot \int _0^3x^2dx\\\mathrm{Apply\:the\:Power\:Rule}:\quad \int x^adx=\frac{x^{a+1}}{a+1}\\=> \pi \left[\frac{x^{2+1}}{2+1}\right]^3_0\\=> \pi \left[\frac{x^3}{3}\right]^3_0\\\mathrm{Compute\:the\:boundaries}: \left[\frac{x^3}{3}\right]^3_0=9\\\mathrm{Substitute:9\pi }[/tex]
As you can tell our solution is option b, 9π. Hope that helps!
Answer:
9π
Step-by-step explanation:
Start by graphing the region. The region bound by y = x, x = 3, and y = 0 is a triangle. When rotated about the x-axis, the resulting shape is a cone.
First, let's find the volume using integration. To do that, slice the cone into circular disks. Each disk has a thickness of dx, and a radius of y. So the volume of each disk is:
dV = π r² h
dV = π y² dx
y = x, so:
dV = π x² dx
The total volume is the sum of all the disks from x=0 to x=3:
V = ∫ dV
V = ∫₀³ π x² dx
Integrating:
V = π/3 x³ |₀³
V = π/3 (3)³ − π/3 (0)³
V = 9π
We can check our answer using geometry. Volume of a cone is:
V = ⅓ π r² h
V = ⅓ π (3)² (3)
V = 9π