Answer:
x = 2 y = 0
Step-by-step explanation:
Answer:
3π square units.
Step-by-step explanation:
We can use the disk method.
Since we are revolving around AB, we have a vertical axis of revolution.
So, our representative rectangle will be horizontal.
R₁ is bounded by y = 9x.
So, x = y/9.
Our radius since our axis is AB will be 1 - x or 1 - y/9.
And we are integrating from y = 0 to y = 9.
By the disk method (for a vertical axis of revolution):
![\displaystyle V=\pi \int_a^b [R(y)]^2\, dy](https://tex.z-dn.net/?f=%5Cdisplaystyle%20V%3D%5Cpi%20%5Cint_a%5Eb%20%5BR%28y%29%5D%5E2%5C%2C%20dy)
So:

Simplify:

Integrate:
![\displaystyle V=\pi\Big[y-\frac{1}{9}y^2+\frac{1}{243}y^3\Big|_0^9\Big]](https://tex.z-dn.net/?f=%5Cdisplaystyle%20V%3D%5Cpi%5CBig%5By-%5Cfrac%7B1%7D%7B9%7Dy%5E2%2B%5Cfrac%7B1%7D%7B243%7Dy%5E3%5CBig%7C_0%5E9%5CBig%5D)
Evaluate (I ignored the 0):
![\displaystyle V=\pi[9-\frac{1}{9}(9)^2+\frac{1}{243}(9^3)]=3\pi](https://tex.z-dn.net/?f=%5Cdisplaystyle%20V%3D%5Cpi%5B9-%5Cfrac%7B1%7D%7B9%7D%289%29%5E2%2B%5Cfrac%7B1%7D%7B243%7D%289%5E3%29%5D%3D3%5Cpi)
The volume of the solid is 3π square units.
Note:
You can do this without calculus. Notice that R₁ revolved around AB is simply a right cone with radius 1 and height 9. Then by the volume for a cone formula:

We acquire the exact same answer.
You would think it was 3 * 12 = 36. Not so. All polygons have to be broken down into some figure that will give 2 dimensions that are at right angles to each other. That would mean that
d1 * d2 = Area for the small polygon
3d1 * 3d2 = area of the larger polygon
What that means is that the area of the larger one is 9 times the smaller one.
Area large = 12 * 9 = 108 square units. <<<<< answer.
If you find this hard to be leave try it with a square.
Suppose you have a square (the small one) that is 3 cm by 3 cm
The small one has an area of 3*3 cm^2 = 9 cm
Now you have another square that is 3 times larger. That means that each side is 3*3 = 9
So s = 9
Area = s^2
Area = 9^2 = 81 cm^2
81 is 9 times larger than 9 just as you would think.
Answer:
108
Step-by-step explanation:
s=18x6
s=108