If [tex]a + ar + ar^{2} + ... = 15[/tex] and [tex]a + ar^{2} + ar^{4} + ar^{6} + ... = 9[/tex], then what is the sum of the geometric series [tex]a + ar^{3} + ar^{6} + ar^{9} + ...[/tex]?

Answers

Answer 1

Notice that

a + ar³ + ar⁶ + ar⁹ + ... = a + r³ (a + ar³ + ar⁶ + ...)

but the grouped sum on the right side is the same as the sum on the left side. This means that, if the sum we want to compute

a + ar³ + ar⁶ + ar⁹ + ...

converges to S, then

S = a + r³ S

Solve for S :

S - r³ S = a

(1 - r³) S = a

S = a/(1 - r³)

Similarly, knowing the value of the first sum, we have

a + ar + ar² + ar³ + ... = a + r (a + ar + ar² + ...)

but we know

a + ar + ar² + ... = 15

so

15 = a + 15r

and knowing the value of the second sum, we have

a + ar² + ar⁴ + ... = a + r² (a + ar² + ar⁴ + ...)

so

9 = a + 9r²

Solve these two equations for a and r :

15 = a + 15r   ⇒   a = 15 - 15r

9 = a + 9r²   ⇒   9 = 15 - 15r + 9r²   ⇒   3r² - 5r + 2 = (3r - 2) (r - 1) = 0

⇒   r = 2/3 or r = 1

We cannot have r = 1, since that would mean

a + a + a + ... = 15

since the left side is adding infinitely many copies of some constant; such a sum can never converge to a finite number. So it must be that r = 2/3, and it follows that a = 15 - 15 (2/3) = 5.

Then the sum we want has a value of

S = 5/(1 - (2/3))³ = 135/19

Answer 2

Answer:

Step-by-step explanation:

  a + ar¹ + ar² + ar³ + ... = 15       #1

r(a + ar¹ + ar² + ar³ + ...) = 15r

       ar¹ + ar² + ar³ + ... = 15r      #2

subtract #2 from #1

a = 15 - 15r

     a + ar² + ar⁴ + ar⁶ + ... = 9         #3

r²(a + ar² + ar⁴ + ar⁶ + ... )= 9r²

         ar² + ar⁴ + ar⁶ + ... = 9r²       #4

subtract #4 from #3

a = 9 - 9r²

15 - 15r = 9 - 9r²

9r² - 15r + 6 = 0

3r² - 5r + 2 = 0

r = (5 ±√(5² - 4(3)(2))) / (2(3)

r = (5 ± 1) / 6

r = 1

or

r = 4/6 = 2/3

if r = 1 then a = 15 - 15(1) = 0 and a series of zeros added together can never equal 15 so r = 2/3 must be true.

a = 15 - 15(2/3) = 5

   a + ar³ + ar⁶ + ar⁹ + ... = C           #5

r³(a + ar³ + ar⁶ + ar⁹ + ...) = Cr³

         ar³ + ar⁶ + ar⁹ + ... = Cr³          #6

subtract #6 from #5

a = C - Cr³

a = C(1 - r³)

C = a/(1 - r³)

C = 5/(1 - (2/3)³)

C = 5/(1 - 8/27)

C = 5/(19/27)

C = 5(27/19)

C = 135/19 = 7.1052631578947368....


Related Questions

Cassidy is selling popcorn for a fundraiser sale at the price shown. he purchases a total of 150 containers of popcorn to sell. after he sells 25 containers, he will make a total profit, after his upfront costs, of $5.50 cassidy's profit, after upfront costs, can be modeled by a linear function in the form of y=mx+b.

C. Will the function be discrete or continuous? Explain.

D. Write the function that models Cassidy's profit.

E. What is the domain of the function?


F. What is Cassidy's profit or loss if he does not sell any popcorn?

G. What is cassidy's profit if he sells all the popcorn?

H. What is the range of the function? ​

Answers

The domain and the range of the function describes the possible profit or

loss from the sale of popcorn and the number of popcorn units.

The correct responses are;

C. The function is discreteD. The function is; y = 1.5·x - 32E. The domain is; 0 ≤ x ≤ 150F. The loss when non of the popcorn is sold is $-32G. The profit is $193H. The range is; -32 ≤ y ≤ 193

Reasons:

The question parameters are;

The price of a popcorn = $1.5

Number of popcorn he purchases = 150

Total profit made = $5.50

The number of containers sold = 25

Therefore;

C. Given that the number of containers sole is countable, the function will be discrete.

D. Cost of the containers = Revenue - Profit

Which gives;

Cost of the containers = 1.5 × 25 - 5.5 = 32

The given function is therefore;

y = 1.5·x - 32

E. The domain is the 150 containers which gives;

The domain = 0 ≤ x ≤ 150

F. When no popcorn is sold, we have;

x = 0, which gives;

y = 1.5 × 0 - 32 = -32

If he does not sell any popcorn, the loss is $32

G. If all the popcorn are sold, we have;

x = 150

Therefore;

y = 1.5 × 150 - 32 = 193

The profit if all the popcorn are sold = $193

H. The range of the function are the possible y values, which is the possible profit or loss, which gives;

The range = -32 ≤ y ≤ 193

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There is a rack of 7 billiards balls, numbered from 1 to 7. If one ball is selected at random, determine the odds against it being an odd-numbered ball.
The odds are 0:0
(Type whole numbers. Simplify your answer.)

Answers

Answer:

Step-by-step explanation:

seven options 1, 2, 3, 4, 5, 6, 7

three successes for it being even. 2, 4, 6

odds are 3:7 of against randomly drawing an odd numbered ball.

9. Sofija buys a bracelet for $14.50 plus 8% tax.
Momoka buys a necklace for $12 plus 8% tax.
Enter the sum, in dollars, that Sofija and
Momoka paid, including tax.

Answers

Answer:

$12.96

Step-by-step explanation:

Before Tax Price: $12.00

Sale Tax: 8.00% or $0.96

After Tax Price: $12.96

The password must consist of a vowel followed by 3 letter and 2 odd digits. How many passwords are possible if repetition is allowed?

Answers

The answer is 2197000

There are 5 vowels, AEIOU

Then followed by 3 letters
There are 26 options for the first letter, second letter and third letter

And then followed by two odd digit, there are 5 odd digits, 1,3,5,7,9

5x26x26x26x5x5 = 2197000


What is the value
of m when p= 32
3p + 2 = m
m =
O
11
00
8
O
5
3

Answers

Just substitute 32 for p in the equation
3(32)+2=m
96+2=m
M=98

Equation 2

T

.

X

-

Show

2(4k + 3) - 13 = 2(18 – k) - 13

Answers

Answer:

Step-by-step

= 2 ( 1 8 − ) − 1 3 -13=2(18-k)-138 + 6 − 1 3

= 2 ( 1 8 − ) − 1 3

in the pediatric unit of a hospital has 165 beds how many are there if each room holds 3 beds

Answers

Answer:

There are 55 rooms

Step-by-step explanation:

There are 165 beds in the hospital. Each room contains 3 beds. In order to find the number of beds per room, take the total number of beds and divide it by the number of rooms in each bed. 165/3=55. There are 55 rooms in the hospital, all containing 3 beds.

Hope this helps!

PLEASE HELP ME!!!!!


Laura earns an hourly rate of $14.50 for the first 40 hours that she works in a week. She earns one- and-a-half times her hourly rate for any hours over 10. If she earned $775.75 in one week, how many hours did she work?

a. 35.7
b. 53.5
c. 45
d. 49​

Answers

Answer:

I'm not 100% sure but I believe the answer is A

The total hours of work done by Laura is 39 hours.

What are Mathematical operators?

A collection of numbers and operations is an expression in mathematics. The following are the parts of a math expression that do a math operation:

Operands: Operands are the numbers that an operator uses. The terms that are given to the operands vary according to the kind of operation.

Given the hourly income Laura = $14.50

total hours she works in a week = 40

increase in rate after working after 10 hours is 1.5 times

the hourly rate after 10 hours = 14.50 x 1.5 = $21.75

amount earned in 10 hours = 10 x 14.5 = $145

total earning = $775.75

the amount left after reducing the amount of 10 hours = 775.75 - 145 = $630.75

$630.75 is earned in = 630.75/21.75 hours = 29 hours

total hours Laura worked = 10 + 29 = 39 hours.

Hence Laura worked 39 hours in a week.

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0.15% of what number is 10.5

Answers

the answer is 7000..

Answer:

70

Step-by-step explanation:

10.5/0.15 = 70

Check:

70 · 0.15 = 10.5

the product of seven non-zero factors. of which only three are positive. is

a) positive
B) negative
c) null​​

Answers

Answer:

The answer is A

Step-by-step explanation:

This is one of those sneaky questions where you think there is no definite answer, but don't despair. There is an answer.

You have 7 numbers

3 of them are positive which means greater than 0. Let's pick them

3 4 5 = 60

That part's easy. Those 3 numbers give a plus result.

Now try the other 4 numbers

-3  - 2  - 1 - 4

Do you see what's going to happen. You have -3 * - 2 = 6

then you get - 1 * - 4 = 4

All of a sudden you get a positive result 6 * 4 = 24

60 * 24 = 1440

So the answer is any 3 plus numbers multiplied by 4 minus numbers gives a plus result.

Answer:

  a) positive

Step-by-step explanation:

If 3 of the 7 numbers are positive, the other 4 are negative. The product of an even number of negative factors is positive. The product of any number of positive factors is positive.

The product is positive.

57846*3746 help please

Answers

Answer:216691116

Step-by-step explanation:

Answer:

216,691,116

Step-by-step explanation:

how to make chicken, with rice ....​

Answers

Answer:

put rice with chicken

Step-by-step explanation:

There are eight swans swimming on a pond and four of those swans are
black. What fraction of the swans are black?

Answers

Answer: A. (4/8)

Step-by-step explanation: If there is 4 black swans and 8 swans in total you could see it's 4 black swan out of 8 total swans. You could do

8/8 - 4/8 = 4/8 to find out the answer too.

Total number of swans= 8
Total no.of black swans= 4
Fraction of black swans among all swans= 4/8
If you simplify 4/8 you will get 1/2, in exam you have to always write the simplified version to get full marks
Hope it helped


-6+ (-19) =
Evaluate

Answers

The answer if you need helo with math like this come to me -25

67*25 helpppp pleaseeee

Answers

Answer:

1675

Step-by-step explanation:

do people not have calculators?

The formula for finding the perimeter of a rectangle is P = 2L + 2W. If a rectangle has a perimeter of 68 inches and the length is 14 inches longer than its width, find the width.

Answers

Answer:

width(w)= 20inches

Step-by-step explanation:

solution,

given,

perimeter of a rectangle (P)=68inches

length of rectangle= 14 inches

we know,

perimeter of a rectangle=2L + 2W

or,68=2×14+2×w

or,68-28=2w

or,40=2w

or,w=40÷2

or,w=20inches.

Rectangle J′K′L′M′ shown on the grid is the image of rectangle JKLM after transformation. The same transformation will be applied on trapezoid STUV.

Rectangle JKLM is drawn on the grid with vertices J at negative 7, negative 6. K is at negative 4, negative 6. L is at negative 4, negative 2. M is at negative 7, negative 2. Rectangle J prime K prime L prime M prime is drawn with vertices J at prime 6, negative 9. K prime is at 9, negative 9. L prime 9, negative 5. M prime is at 6, negative 5. Trapezoid STUV is drawn with vertices at S 3, 2. T is at 5, 5. U is at 2, 6. V is at 1, 4.

What will be the location of T′ in the image trapezoid S′T′U′V′?

(18, −2)
(18, 2)
(15, −2)
(15, 2)

Answers

The transformed figure has the opposite orientation (A'B'C'D' is counterclockwise, whereas ABCD is clockwise), so a reflection is involved. The segment C'D' is still at the bottom, as is CD, so the reflection must be across a vertical line.

In the attached, the light-blue figure A''B''C''D'' shows the reflection of ABCD across the y-axis. It is easy to see that figure A'B'C'D' is a translation of that 5 units downward.

The appropriate choice is the 2nd one ...

... Reflection over the y-axis followed by a translation down by 5 units. droiyhjfgmdp[ytijkmrdo[ijy[hjmpoiujhokmonj-oimog[fujyjh[opifj[yuj'hkm[ofidyjhoijpofyijh[foist[Yaj[hkmcf[oiyjnjc[city[huff[pay[Pj[ifcjty[ijh[fjotijyh[Hj[fogyish[coif[t0yju[pick[fujph[fj0yh-hifcj[oijhpoijcoijhpouihughdxoiuhtoutpgoindxhouthughxdiurht09uhdxpjrtnhiuhdxiourth8iuthojucfptui9yhufchouihgcifuygtidhiougocdiudrhtudxhfogiurhtiohgcdoiuhoiuxdrhtoiughoiutdgr8uhseoiuhtdiuhroiuiudxdhgioudhugtoirugiudghxtiugdifurtyioudfxhriuytoduyhxotuyotiugoiutyoiuhrtuoihesoitughedugyhoiduhrtouhoiguhoidruthuihgdoiuhrtouighdoiurhtghoidutrhourthiuhdcoiutrioduhtgoiuhoitdrhgiouhoiuhderytgiudyhi8yetgiydhrugterudsoseoysrtgoivdxuht8ygfodushty8ugf9d8sythuygsd9e8tgoyfsdgtofidugsyt8g9s8ewgutiyges8tgiueysg7iygterysgt8t6yoesut


A movie theater is splitting
cups 30 of popcorn into 18
bags. How much popcorn
will each bag holde

Answers

Answer:

30/18=1 2/3 cups of popcorn in each bag

Hope This Helps!!!

Caleb’s receipt for lunch is shown below is Caleb pays with a $10 bill how much change will he receive

Answers

Answer:

Please attach the screenshot for the receipt so people can answer

Answer:

3.08                      

 

Explanation

                           

3.79

+1.45

 1.24

-----------

6.53

+ .39

-----------

6.92                Now  

                              10.00

                             - 6.92

                            3.08

2. Use the conversion table to convert the following metric units into the given English units.
Round your answers to two decimal places.
a. 12 mm to inches
b. 75 km to miles
C. 150 m to feet
d. 63 square meters to square feet
e 45 meters per second to feet per second
1.9 L (liters) to U.S.quarts

Answers

Answer:

I need only 5 brainlisted please give me

Step-by-step explanation:

please anyone please I request you all

The conversion is a. 12 mm ≈ 0.47 inches

b. 75 km ≈ 46.60 miles

c. 150 m ≈ 492.13 feet

d. 63 square meters ≈ 678.13 square feet

e. 45 meters per second ≈ 147.64 feet per second

f. 1.9 L ≈ 2.01 U.S. quarts

To convert the metric units into the given English units, we'll use the following conversion factors:

1 inch = 25.4 mm

1 mile = 1.60934 km

1 meter = 3.28084 feet

1 square meter = 10.7639 square feet

1 meter per second = 3.28084 feet per second

1 liter = 1.05669 U.S. quarts

a. 12 mm to inches:

12 mm * (1 inch / 25.4 mm) ≈ 0.47 inches

b. 75 km to miles:

75 km * (1 mile / 1.60934 km) ≈ 46.60 miles

c. 150 m to feet:

150 m * (3.28084 feet / 1 meter) ≈ 492.13 feet

d. 63 square meters to square feet:

63 square meters * (10.7639 square feet / 1 square meter) ≈ 678.13 square feet

e. 45 meters per second to feet per second:

45 meters per second * (3.28084 feet per second / 1 meter per second) ≈ 147.64 feet per second

f. 1.9 L (liters) to U.S. quarts:

1.9 L * (1.05669 U.S. quarts / 1 liter) ≈ 2.01 U.S. quarts

So, after rounding to two decimal places:

a. 12 mm ≈ 0.47 inches

b. 75 km ≈ 46.60 miles

c. 150 m ≈ 492.13 feet

d. 63 square meters ≈ 678.13 square feet

e. 45 meters per second ≈ 147.64 feet per second

f. 1.9 L ≈ 2.01 U.S. quarts

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A man walks 10 km, then travels a certain distance by train and then by bus as far as twice by the train. If the whole journey is of 70km, how far did he travel by train?​

Answers

Answer:

The man traveled 20km by train.

Step-by-step explanation:

If x is the distance he traveled by train, you can write this equation to represent the situation:

[tex]10+x+2x=70[/tex]

Then, you can simply solve for x:

[tex]10+3x=70\\3x=60\\x=20[/tex]

The man traveled 20km by train.

[tex]10+(20)+2(20)=70\\10+20+40=70\\70=70[/tex]

Solve it (Easy question) :
[tex]\lim_{x \rightarrow 1} \cfrac{x {}^{2} - 25 }{x {}^{2} - 5 }[/tex]

Answers

The solution to the limit expression [tex] \lim_{x \to 1} \frac{x^2 - 25}{x - 5} [/tex] is 6

The limit expression is given as:

[tex] \lim_{x \to 1} \frac{x^2 - 25}{x - 5}[/tex]

Express 25 as 5^2

[tex] \lim_{x \to 1} \frac{x^2 - 5^2}{x - 5}[/tex]

Express the numerator as the difference of two squares

[tex] \lim_{x \to 1} \frac{x^2 - 25}{x - 5} = \lim_{x \to 1} \frac{(x - 5)(x +5)}{x - 5}[/tex]

Evaluate the quotient

[tex] \lim_{x \to 1} \frac{x^2 - 25}{x - 5} = \lim_{x \to 1} (x +5)[/tex]

Remove bracket

[tex] \lim_{x \to 1} \frac{x^2 - 25}{x - 5} = \lim_{x \to 1} x +5\\ [/tex]

Substitute 1 for x

[tex] \lim_{x \to 1} \frac{x^2 - 25}{x - 5} = 1 +5[/tex]

[tex] \lim_{x \to 1} \frac{x^2 - 25}{x - 5} = 6[/tex]

Hence, the solution to the limit expression [tex] \lim_{x \to 1} \frac{x^2 - 25}{x - 5} [/tex] is 6

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7. Which of the lists of three lengths cannot form a triangle?
7,7,20
13,13, 20
13,13,13
7,7,7
7,13,13

Answers

Answer:

7,7,20 I think

Step-by-step explanation:

7+7 is less then 20

in the actual room, the distance between the front and back walls is 8 feet. what is the actual length of the front wall, in feet?

Answers

Answer:

8 feet

Step-by-step explanation:

it actually will be 8 feet

find the following right triangle, find the side length x

Answers

Answer:

x=41

Step-by-step explanation:

9²+40²=x²

81+1600=x²

1681=x²

√1681=√x²

41=x

What is -3/4+2 3/4 O 3 1/2 O 3 3/4 O 2 1/2 O 2​

Answers

Answer:

D. 2

Step-by-step explanation:

Common denominator is already presented which is 4.

-3/4 and 3/4 cancel each other out.

you can also convert to decimal form -3/4 + 2 3/4 is the same as:

-0.75 + 2.75 = 2.

h=-16t^2+72t+100 solve for t

Answers

Answer:0

Step-by-step explanation:

hey i'm in the six grade i'm not sure but pls try it

3. Let Angle ABC be an isosceles triangle with AB = AC. Which of the following describes
LB of the triangle?
A. Exterior Angle
B. Base Angle
C. Vertex Angle
D. Remote Interior Angle

Will mark Brainiest

Answers

Answer:
It’s should be D because
Step by step explanation

find the angle of rotation that maps point D onto point A

Answers

Answer:

A - 144

Step-by-step explanation:

everything else would be too far. thx

3. A rectangular deck has an area of 24 square yards. The length of the deck is shown in the figure. What is the width of the deck in yards? Enter your answer in the box.

Answers

Answer:

can you please send the picture as well because for this

(The length of the deck is shown in the figure.=??)

figure is needed ..

Tell me the figure but rectangular deck has area 24 use rectangle formula b(h)= area or lwh=area
But we already know the Area
lwh=24
But I don't see the length of the deck that shown in the figure

Sorry you don't have enough information
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