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3 years ago

If n is a term of the sequence 2,5,8,11,..., which expression would give the value of n?

Mathematics

2 answers:

Wittaler [7]3 years ago

5 0

The term of the sequence is eleven 11

Elina [12.6K]3 years ago

4 0

First Find the difference between the numbers, in this case it's 3, then multiply it by n, so first you have 3n. Now, subtract this number from the first term, and put it on the end of your equation. Here we get -1. So the answer is 3n-1

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A window is 21 inches wide, and its perimeter is 112 inches. What is the length of the window?

Kazeer [188]

Answer:

The length of the window is 35 inches.

Step-by-step explanation:

Perimeter of an object can be found using the general formula: P = 2W + 2L, where P = perimeter, W = width and L= length. Since both the width and perimeter of the window are given, we can plug these values into the formula to solve for the missing variable 'L': 112 = 2(21) + 2L, or 112 = 42 + 2L. We can then use inverse (opposite) operations to isolate the variable and solve. Whatever we do to one side of the equation, we do to the other. We will start by subtracting 42 from each side: 112 - 42 = 42 - 42 + 2L or 70 = 2L. Next, we divide both sides by 2 to solve for L: 70/2 = 2L/2 or L = 35. So, the final length of the window is 35 inches.

8 0

3 years ago

16) (1 Point) : Solve the equation

Marat540 [252]

Answer:

(B)

4 +/- 3 sqrt(2) or 4+3sqrt(2) and 4-3sqrt(2)

Step-by-step explanation:

4(c-4)^2=72

4(c-4)(c-4)=72

foil the parenthesis (first, outside, inside, last)

4(c^2 -4c -4c +16)=72

4(c^2-8c+16)=72

divide each side by 4

c^2-8c+16=18

subtract 18 from both sides

c^2-8c-2

use quadratic formula

((-b +/- sqrt((-b^2)-4ac)))/2a

((-(-8)+/-sqrt((-8)^2-4(1)(-2)))/2(1))

(8+/-sqrt(64-(-8)))/2

(8+/-sqrt(64+8))/2

(8+/-sqrt(72))/2

(8+/-sqrt(36 * 2))/2

(8+/-6sqrt(2))/2

4+/-3sqrt(2)

or 4+3sqrt(2) and 4-3sqrt(2)

3 0

2 years ago

Find the Fourier series of f on the given interval. f(x) = 1, ?7 < x < 0 1 + x, 0 ? x < 7

Zolol [24]

$f(x)=\begin{cases}1&\text{for }-7$

The Fourier series expansion of $f(x)$ is given by

$\dfrac{a_0}2+\displaystyle\sum_{n\ge1}a_n\cos\frac{n\pi x}7+\sum_{n\ge1}b_n\sin\frac{n\pi x}7$

where we have

$a_0=\displaystyle\frac17\int_{-7}^7f(x)\,\mathrm dx$
$a_0=\displaystyle\frac17\left(\int_{-7}^0\mathrm dx+\int_0^7(1+x)\,\mathrm dx\right)$
$a_0=\dfrac{7+\frac{63}2}7=\dfrac{11}2$

The coefficients of the cosine series are

$a_n=\displaystyle\frac17\int_{-7}^7f(x)\cos\dfrac{n\pi x}7\,\mathrm dx$
$a_n=\displaystyle\frac17\left(\int_{-7}^0\cos\frac{n\pi x}7\,\mathrm dx+\int_0^7(1+x)\cos\frac{n\pi x}7\,\mathrm dx\right)$
$a_n=\dfrac{9\sin n\pi}{n\pi}+\dfrac{7\cos n\pi-7}{n^2\pi^2}$
$a_n=\dfrac{7(-1)^n-7}{n^2\pi^2}$

When $n$ is even, the numerator vanishes, so we consider odd $n$ , i.e. $n=2k-1$ for $k\in\mathbb N$ , leaving us with

$a_n=a_{2k-1}=\dfrac{7(-1)-7}{(2k-1)^2\pi^2}=-\dfrac{14}{(2k-1)^2\pi^2}$

Meanwhile, the coefficients of the sine series are given by

$b_n=\displaystyle\frac17\int_{-7}^7f(x)\sin\dfrac{n\pi x}7\,\mathrm dx$
$b_n=\displaystyle\frac17\left(\int_{-7}^0\sin\dfrac{n\pi x}7\,\mathrm dx+\int_0^7(1+x)\sin\dfrac{n\pi x}7\,\mathrm dx\right)$
$b_n=-\dfrac{7\cos n\pi}{n\pi}+\dfrac{7\sin n\pi}{n^2\pi^2}$
$b_n=\dfrac{7(-1)^{n+1}}{n\pi}$

So the Fourier series expansion for $f(x)$ is

$f(x)\sim\dfrac{11}4-\dfrac{14}{\pi^2}\displaystyle\sum_{n\ge1}\frac1{(2n-1)^2}\cos\frac{(2n-1)\pi x}7+\frac7\pi\sum_{n\ge1}\frac{(-1)^{n+1}}n\sin\frac{n\pi x}7$