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drek231 [11]
2 years ago
6

Calculus Problem

Mathematics
1 answer:
Roman55 [17]2 years ago
7 0

The two parabolas intersect for

8-x^2 = x^2 \implies 2x^2 = 8 \implies x^2 = 4 \implies x=\pm2

and so the base of each solid is the set

B = \left\{(x,y) \,:\, -2\le x\le2 \text{ and } x^2 \le y \le 8-x^2\right\}

The side length of each cross section that coincides with B is equal to the vertical distance between the two parabolas, |x^2-(8-x^2)| = 2|x^2-4|. But since -2 ≤ x ≤ 2, this reduces to 2(x^2-4).

a. Square cross sections will contribute a volume of

\left(2(x^2-4)\right)^2 \, \Delta x = 4(x^2-4)^2 \, \Delta x

where ∆x is the thickness of the section. Then the volume would be

\displaystyle \int_{-2}^2 4(x^2-4)^2 \, dx = 8 \int_0^2 (x^2-4)^2 \, dx \\\\ = 8 \int_0^2 (x^4-8x^2+16) \, dx \\\\ = 8 \left(\frac{2^5}5 - \frac{8\times2^3}3 + 16\times2\right) = \boxed{\frac{2048}{15}}

where we take advantage of symmetry in the first line.

b. For a semicircle, the side length we found earlier corresponds to diameter. Each semicircular cross section will contribute a volume of

\dfrac\pi8 \left(2(x^2-4)\right)^2 \, \Delta x = \dfrac\pi2 (x^2-4)^2 \, \Delta x

We end up with the same integral as before except for the leading constant:

\displaystyle \int_{-2}^2 \frac\pi2 (x^2-4)^2 \, dx = \pi \int_0^2 (x^2-4)^2 \, dx

Using the result of part (a), the volume is

\displaystyle \frac\pi8 \times 8 \int_0^2 (x^2-4)^2 \, dx = \boxed{\frac{256\pi}{15}}}

c. An equilateral triangle with side length s has area √3/4 s², hence the volume of a given section is

\dfrac{\sqrt3}4 \left(2(x^2-4)\right)^2 \, \Delta x = \sqrt3 (x^2-4)^2 \, \Delta x

and using the result of part (a) again, the volume is

\displaystyle \int_{-2}^2 \sqrt 3(x^2-4)^2 \, dx = \frac{\sqrt3}4 \times 8 \int_0^2 (x^2-4)^2 \, dx = \boxed{\frac{512}{5\sqrt3}}

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Which graph represents the solution set of the system of inequalities? {x+y<12 y≥x−4
RSB [31]

Answer: The graph in the bottom right-hand corner

(see figure 4 in the attached images below)

===========================================

Explanation:

Let's start off by graphing x+y < 1. The boundary equation is x+y = 1 since we simply change the inequality sign to an equal sign. Solve for y to get x+y = 1 turning into y = -x+1. This line goes through (0,1) and (1,0). The boundary line is a dashed line due to the fact that there is no "or equal to" in the original inequality sign. So x+y < 1 turns into y < -x+1 and we shade below the dashed line. The "less than" means "shade below" when y is fully isolated like this. See figure 1 in the attached images below.

Let's graph 2y >= x-4. Start off by dividing everything by 2 to get y >= (1/2)x-2. The boundary line is y = (1/2)x-2 which goes through the two points (0,-2) and (4,0). The boundary line is solid. We shade above the boundary line. Check out figure 2 in the attached images below.

After we graph each individual inequality, we then combine the two regions on one graph. See figure 3 below. The red and blue shaded areas in figure 3 overlap to get the purple shaded area you see in figure 4, which is the final answer. Any point in this purple region will satisfy both inequalities at the same time. The solution point cannot be on the dashed line but it can be on the solid line as long as the solid line is bordering the shaded purple region. Figure 4 matches up perfectly with the bottom right corner in your answer choices.

5 0
3 years ago
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I need an answer ASAP pls
tino4ka555 [31]

Answer:

Age 42 salary 30,000

Step-by-step explanation:

He had to restart his medical training, therefore, making him have a lower salary regardless of his age, making this point an obvious outlier

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3 years ago
Alguem me ajuda<br>por favor​
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Answer:

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ValentinkaMS [17]

Answer:

Pi x (2 x radius) = C

Step-by-step explanation:

Learn that the perimeter of a circle has its own special name, called "circumference." The symbol is a capital C. It is calculated using the formula Pi x diameter, or 3.14 x d = C. It can also be calculated by Pi x (2 x radius) = C or 3.14 x (2 x r) = C.

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2 years ago
HELP HELP HELP!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Arrange the functions in ascending order, starting with the function t
san4es73 [151]
If x is squared, that will be biggest by the end because it gets bigger the quickest. x^2 + 4 is always 4 greater than x^2, no matter what the value of x is.

5x+3 is always 3 greater than 5x also.

Besides that, you can rank them based on their slopes (5x < 7x < 8x, etc.)

So,
5x
5x + 3
7x
8x + 3
x^2
x^2 + 4

You can also just say “eventually” means that they’re asking to find the values of each when x is really big. so just choose x=100, and plug that into each one.

So, to check that order:
5(100) = 500
5(100) + 3 = 503
7(100) = 700
8(100) + 3 = 803
(100)^2 = 10,000
(100)^2 + 4 = 10,004

Those are in ascending order, so that must be the right order!
6 0
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