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3 years ago

Given a geometric sequence in the table below, create the explicit formula and list any restrictions to the domain.

Mathematics

2 answers:

weeeeeb [17]3 years ago

4 0

Answer:

Step-by-step explanation:

given the first 3 terms of the geometric sequence - 4, 20, - 100

with r = $\frac{-100}{20}$ = $\frac{20}{-4}$ = - 5

the n th term formula ( explicit formula ) is

$a_{n}$ = $a_{1}$ $r^{n-1}$

here r = - 5 and $a_{1}$ = - 4, hence

$a_{n}$ = - 4 $(-5)^{n-1}$ with n ≥ 1

pishuonlain [190]3 years ago

4 0

Answer:

answer would be b.

Step-by-step explanation:

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Empirical rule (statistics)Help please!!!

emmasim [6.3K]

The empirical rule you're referring to is the 68-95-99.7 rule, which asserts that for a normal (bell-shaped) distribution, approximately 68% of the distribution lies within 1 standard deviation of the mean; 95% lies within 2 standard deviations of the mean; and 99.7% lies within 3 standard deviations of the mean.

Let $X$ be the random variable denoting vehicle speeds along this highway. We want to find $P(61$ . To use the rule, we need to rephrase this probability in terms of the mean and standard deviation.

Notice that $61=70-9=70-3\cdot3$ , and $79=70+9=70+3\cdot3$ . In other words, 61 and 79 both lie exactly 3 standard deviations away from the mean, so $P(61$ .

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3 years ago

How to know if a function is periodic without graphing it ?

zhenek [66]

A function $f(t)$ is periodic if there is some constant $k$ such that $f(t+k)=f(k)$ for all $t$ in the domain of $f(t)$ . Then $k$ is the "period" of $f(t)$ .

Example:

If $f(x)=\sin x$ , then we have $\sin(x+2\pi)=\sin x\cos2\pi+\cos x\sin2\pi=\sin x$ , and so $\sin x$ is periodic with period $2\pi$ .

It gets a bit more complicated for a function like yours. We're looking for $k$ such that

$\pi\sin\left(\dfrac\pi2(t+k)\right)+1.8\cos\left(\dfrac{7\pi}5(t+k)\right)=\pi\sin\dfrac{\pi t}2+1.8\cos\dfrac{7\pi t}5$

Expanding on the left, you have

$\pi\sin\dfrac{\pi t}2\cos\dfrac{k\pi}2+\pi\cos\dfrac{\pi t}2\sin\dfrac{k\pi}2$

and

$1.8\cos\dfrac{7\pi t}5\cos\dfrac{7k\pi}5-1.8\sin\dfrac{7\pi t}5\sin\dfrac{7k\pi}5$

It follows that the following must be satisfied:

$\begin{cases}\cos\dfrac{k\pi}2=1\\\\\sin\dfrac{k\pi}2=0\\\\\cos\dfrac{7k\pi}5=1\\\\\sin\dfrac{7k\pi}5=0\end{cases}$

The first two equations are satisfied whenever $k\in\{0,\pm4,\pm8,\ldots\}$ , or more generally, when $k=4n$ and $n\in\mathbb Z$ (i.e. any multiple of 4).

The second two are satisfied whenever $k\in\left\{0,\pm\dfrac{10}7,\pm\dfrac{20}7,\ldots\right\}$ , and more generally when $k=\dfrac{10n}7$ with $n\in\mathbb Z$ (any multiple of 10/7).

It then follows that all four equations will be satisfied whenever the two sets above intersect. This happens when $k$ is any common multiple of 4 and 10/7. The least positive one would be 20, which means the period for your function is 20.

Let's verify:

$\sin\left(\dfrac\pi2(t+20)\right)=\sin\dfrac{\pi t}2\underbrace{\cos10\pi}_1+\cos\dfrac{\pi t}2\underbrace{\sin10\pi}_0=\sin\dfrac{\pi t}2$

$\cos\left(\dfrac{7\pi}5(t+20)\right)=\cos\dfrac{7\pi t}5\underbrace{\cos28\pi}_1-\sin\dfrac{7\pi t}5\underbrace{\sin28\pi}_0=\cos\dfrac{7\pi t}5$

More generally, it can be shown that

$f(t)=\displaystyle\sum_{i=1}^n(a_i\sin(b_it)+c_i\cos(d_it))$

is periodic with period $\mbox{lcm}(b_1,\ldots,b_n,d_1,\ldots,d_n)$ .

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3 years ago

Julie needs to cut 4 pieces of yam, each with the same length, and a piece of yarn 7.75 inches long. Let x represent the

Lapatulllka [165]

Answer:

She has to cut another piece = 7.75 inches

Total length = 4x + 7.75

This is what y represent, so

y = 4x + 7.75

The graph of the equation is continuous

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3 years ago

This year 426,731 people visited a water park.last year 102,865 fewer people visited the park the year the park opened 84,007 fe

mylen [45]

Answer:

236,859 people visited the water park the year it opened.

Step-by-step explanation:

426,731 - 102,865= 323,866 the amount of people that visited last year

323,866 - 87,007 = 236,859 the amount of people that visited the water park the year it opened

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3 years ago

Abby can buy an 8-pound bag of dog food for $7.40 or a 4- pound of the same dog food for 5.38. Which is better buy?

My name is Ann [436]

The answer to your Q the better one it is the 4- pound bag because it coast less money

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3 years ago