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3 years ago

there are about 100 million smartphones in the U.S. your teacher has one smartphone. what share of US smartphones does your teac

her have? express your answer using a negative power of 10.

Mathematics

1 answer:

barxatty [35]3 years ago

3 0

$100 000 000 = 10^{8}$

$\frac{1}{100 000 000} = 10^{-8}$

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Simplify the expressions:

Blizzard [7]

Answer:

a. (7x²+2) + (2x²+3)

= 9x² + 5

b. (5x + 2) + (8x + 3)

= 13x +5

c. (5x)(8x + 3)

= 40x² + 15x

7 0

1 year ago

Rewrite the following integral in spherical coordinates.

lora16 [44]

In cylindrical coordinates, we have $r^2=x^2+y^2$ , so that

$z = \pm \sqrt{2-r^2} = \pm \sqrt{2-x^2-y^2}$

correspond to the upper and lower halves of a sphere with radius $\sqrt2$ . In spherical coordinates, this sphere is $\rho=\sqrt2$ .

$1 \le r \le \sqrt2$ means our region is between two cylinders with radius 1 and $\sqrt2$ . In spherical coordinates, the inner cylinder has equation

$x^2+y^2 = 1 \implies \rho^2\cos^2(\theta) \sin^2(\phi) + \rho^2\sin^2(\theta) \sin^2(\phi) = \rho^2 \sin^2(\phi) = 1 \\\\ \implies \rho^2 = \csc^2(\phi) \\\\ \implies \rho = \csc(\phi)$

This cylinder meets the sphere when

$x^2 + y^2 + z^2 = 1 + z^2 = 2 \implies z^2 = 1 \\\\ \implies \rho^2 \cos^2(\phi) = 1 \\\\ \implies \rho^2 = \sec^2(\phi) \\\\ \implies \rho = \sec(\phi)$

which occurs at

$\csc(\phi) = \sec(\phi) \implies \tan(\phi) = 1 \implies \phi = \dfrac\pi4+n\pi$

where $n\in\Bbb Z$ . Then $\frac\pi4\le\phi\le\frac{3\pi}4$ .

The volume element transforms to

$dx\,dy\,dz = r\,dr\,d\theta\,dz = \rho^2 \sin(\phi) \, d\rho \, d\theta \, d\phi$

Putting everything together, we have

$\displaystyle \int_0^{2\pi} \int_1^{\sqrt2} \int_{-\sqrt{2-r^2}}^{\sqrt{2-r^2}} r \, dz \, dr \, d\theta = \boxed{\int_0^{2\pi} \int_{\pi/4}^{3\pi/4} \int_{\csc(\phi)}^{\sqrt2} \rho^2 \sin(\phi) \, d\rho \, d\phi \, d\theta} = \frac{4\pi}3$

4 0

2 years ago

Create a system of equations

Vika [28.1K]

Answer:

Answer: Janet is 16, and David is 11.

Step-by-step explanation:

Let the ages be j and d.

j = d + 5

j + d = 27

Substitute d + 5 for j in the second equation.

d + 5 + d = 27

2d + 5 = 27

2d = 22

d = 11

Substitute 11 for d in the first equation.

j = d + 5

j = 11 + 5

j = 16

Answer: Janet is 16, and David is 11.

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3 years ago

Which ordered pair is a solution of the equation −1/4x + 6 = y?

il63 [147K]

Answer:

Step-by-step explanation:

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3 years ago

Find the simple interest for $3200 invested at 7% for 2 years.

Artemon [7]

Answer:

$448

Step-by-step explanation:

First, converting R percent to r a decimal

r = R/100 = 7%/100 = 0.07 per year,

then, solving our equation

I = 3200 × 0.07 × 2 = 448

I = $ 448.00

USE THE EQUATION Interest= Principal x rate x time

3 0

3 years ago