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Roman55 [17]
3 years ago
9

Can someone help me with 21

Mathematics
1 answer:
Darina [25.2K]3 years ago
3 0
B cuz we *3*3*3 to reach to n 7
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Part 2
ahrayia [7]

Answer:

B. 236.3

Step-by-step explanation:

Population density can be found by dividing the number of people by the area of the land.

number of people / land area

The population is 20,510 people and the area is 86.8 square miles.

20,510 people / 86.8 square miles

Divide 20,510 by 86.8

236.290323 people /square mile

Round to the nearest tenth. The 9 in the hundredth place tell us to round the 2 to a 3 in the tenth place.

236.3 people/ square mile

There are 236.3 people per square mile and B is correct.

6 0
3 years ago
Are all horizontal lines parallel
miskamm [114]
<span>By definition, lines are parallel if they have the same gradient (slope). Any horizontal line has a gradient of 0, so it is parallel to any other horizontal line</span>
7 0
3 years ago
Use cylindrical coordinates. find the volume of the solid that lies within both the cylinder x2 y2 = 9 and the sphere x2 y2 z2 =
marissa [1.9K]
In Cartesian coordinates, the region is given by -3\le x\le3, -\sqrt{9-x^2}\le y\le\sqrt{9-x^2}, and -\sqrt{16-x^2-y^2}\le z\le\sqrt{16-x^2-y^2}. Converting to cylindrical coordinates, using

\begin{cases}\mathbf x(r,\theta,\zeta)=r\cos\theta\\\mathbf y(r,\theta,\zeta)=r\sin\theta\\\mathbf z(r,\theta,\zeta)=\zeta\end{cases}

we get a Jacobian determinant of r, and the region is given in cylindrical coordinates by 0\le\theta\le2\pi, 0\le r\le3, and -\sqrt{16-r^2}\le z\le\sqrt{16-r^2}.

The volume is then

\displaystyle\int_{\theta=0}^{\theta=2\pi}\int_{r=0}^{r=3}\int_{z=-\sqrt{16-r^2}}^{z=\sqrt{16-r^2}}r\,\mathrm dz\,\mathrm dr\,\mathrm d\theta=\dfrac{4(64-7\sqrt7)\pi}3
6 0
3 years ago
(02.03)
RoseWind [281]

Answer:

It's the one under the one you have selected.

Step-by-step explanation:

7:2

14:4

28:8

56:16

Divide the first number by 7 then multiply it by 2.

Example: 56/7=8, 8*2=16 so it's correct.

4 0
3 years ago
Read 2 more answers
HELP!!
leonid [27]

Answer:

The focus point is (2 , 0) ⇒ answer D

Step-by-step explanation:

* Lets revise the equation of the parabola in standard form

- The standard form is (x - h)² = 4p(y - k)

- The focus is (h, k + p)

- The directrix is y = k - p

- If the parabola is rotated so that its vertex is (h , k) and its axis of

 symmetry is parallel to the x-axis, it has an equation of

 (y - k)² = 4p(x - h)

- The focus is (h + p, k)

- The directrix is x = h - p

* Lets solve the problem

∵ The equation of the parabola is y = 1/8(x² - 4x - 12)

- Lets make x² - 4x completing square

∵ √x² = x  

∴ The 1st term in the bracket is x

∵ 4x ÷ 2 = 2x

∴ The product of the 1st term and the 2nd term is 2x

∵ The 1st term is x

∴ the second term = 2x ÷ x = 2

∴ The bracket is (x - 2)²

∵  (x - 2)² = (x² - 4x + 4)

∴ To complete the square add 4 to the bracket and subtract 4 out  

  the bracket to keep the equation as it

∴ (x² - 4x + 4) - 4 = (x - 2)² - 4

- Lets put the equation after making the completing square

∴ y = 1/8 [(x - 2)² - 4 - 12]

∴ y = 1/8 [(x - 2)² - 16] ⇒ multiply both sides by 8

∴ 8y = (x - 2)² - 16 ⇒ add 16 to both sides

∴ 8y + 16 = (x - 2)² ⇒ take from the left side 8 as a common factor

∴ 8(y + 2) = (x - 2)²

∴ The standard form of the equation of the parabola is

   (x - 2)² = 8(y + 2)

∵ The standard form of the equation is (x - h)² = 4p(y - k)

∴ h = 2 , k = -2 , 4p = 8

∵ The focus is (h , k + p)

∵ h = 2

∵ 4p = 8 ⇒ divide both sides by 4

∴ p = 2

∴ The focus = (2 , -2 + 2) = (2 , 0)

* The focus point is (2 , 0)

6 0
3 years ago
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