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....


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Answer:

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Step-by-step explanation:

4 skittles and one being green

Answer:

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Step-by-step explanation:

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Step-by-step explanation:

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Answer:

Genes are DNA transferred to off spring by parents

Answer:

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Step-by-step explanation:

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It is not A because it does not make sense and does not match up.

It Is not C because that is just points and it is asking for a function.

D is wrong.

So It is B.

Here is the graph for B. It matches up.

[tex]\mathrm{Axis\:interception\:points\:of}\:2x-1:\quad \mathrm{X\:Intercepts}:\:\left(\frac{1}{2},\:0\right),\:\mathrm{Y\:Intercepts}:\:\left(0,\:-1\right)[/tex]

[tex]\mathrm{Slope\:of\:}2x-1:\quad m=2[/tex]

I NEED HELP WITH THESE
I am pretty sure of my answers, so I just need someone to double check. Explanation is not needed because I know how to solve it, just needs to be checked. You can put one it you want.

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Answer:

(b) 500 km (b) 6 seconds

Step-by-step explanation:

1.

The semi-major axis length is √47196900 = 6870 km. That distance from the center of the Earth means the satellite is ...

  6780 -6370 = 500 . . . km

from the surface of the Earth.

The satellite is a maximum of 500 km from the Earth.

(It is a minimum of 250 km from Earth.)

__

2.

The equation has a zero at t=6. When the car's velocity is zero, it is at a complete stop.

The car comes to a complete stop when time is 6 seconds.

(The car is still being accelerated, so it doesn't stay stopped.)

__

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Solve the inequality below for t.
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Answer:

T is =/> 3

Step-by-step explanation:

Add 9t to both sides, 3-4t>/= -9 . Subtract 3 from both sides. -4t>/=-12

divide 12 by 4 for 3. Because 3 results in equality between both sides, it is equal, however if t is greater than 3, the lefthand side becomes greater than the right.

factor this polynomial completely x^2-10x+25

Answers

x^2-10x+25

=x^2-5x-5x+25

x(x-5)-5(x-5)

=(x-5)(x-5)

x=5 , x=5

hope it's helpful to you

[tex]x^2 -10x +25\\\\=x^2 -2 \cdot 5 \cdot x +5^2\\\\=(x-5)^2\\\\=(x-5)(x-5)[/tex]

Aarón rides his bike away from home at a constant speed he stops at the park for a while before riding back home at a constant speed

Answers

Answer:

Step-by-step explanation: This is the answer

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Answer:

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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.

Jake ran 4% miles in % of an hour. How fast did he run in one hour?

Answers

5% I don’t really know but I did this by hope it helps

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Answer:

all the numbers +

Step-by-step explanation:

The answer is 10, x=10

A builder makes a certain type of concrete by mixing together 1 part portland cement (made from lime and clay), 3 parts sand, and 5 parts crushed stone. If 765 ft^3 of concrete are needed, how many cubic feet of each ingredient does he need?

Answers

Answer:

85 ft^3 portland cement255 f^3 sand425 ft^3 crushed stone

Step-by-step explanation:

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Answers

Answer:

S 32, W 128, M 96

Step-by-step explanation:

W = 4S

S = 1/3M, or 3S = M

S + W + M = 256

Substitute

S + 4S + 3S = 256

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S = 32

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Sammy's Chipmunk & Squirrel Observations
For a science project, Sammy observed a chipmunk and a squirrel stashing
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Answers

Answer:12 accorns

Step-by-step explanation:

If they each hid the same number of acorns, although the squirrel needed 4 fewer holes, the chipmunk hid 3 acorns in each hole

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i'd appreciate someones help !!!

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The third number is for angle z.
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The size of each area is 3x

Word problems in mathematics involve arithmetic operations and algebraic equations employed to solve real-life cases.

From the given parameters.

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How do you divide fractions? Can someone please explain step by step to get marked as brainliest!

Answers

When diving fractions, use KFC:

K eep the first fraction the same

F lip the second fraction upside down

C hange the divide sign to a multiply

After, just work it out multiplying the denominators and the numerators together getting your answer

Hope this helped you, have a good day bro cya)

Use KCF:
K: Keep ( keep the first fraction the same)
C: Change (change your division sign to a multiplication sign)
F: Flip (flip your second faction numbers)

Ex.
Equation: 3/5 divided by 2/6
KCF: 3/5 multiplied by 6/2

Hope this helps!

14 divided 4 and 7/8 written in simplest form

Answers

Answer:

7 and that is its simplest form

Step-by-step explanation:

thank me later

Answer:

4

Step-by-step explanation:

14 ÷ 4 = 3.5

3.5 and 7/8 = 4

x and y simplifying problem. Please explain how to do thiese. I will gove 15 points

Answers

[tex]\dfrac 56 x + \dfrac25 y - \dfrac14 x + \dfrac3{10} y[/tex]

First, combine like terms:

[tex]\left(\dfrac 56 - \dfrac14\right) x + \left(\dfrac25 + \dfrac3{10}\right)y[/tex]

Now just simplify the coefficients of x and y. We do this by converting each pair of fractions to ones with a common denominator. Then we can combine them easily.

[tex]\dfrac56 - \dfrac14 = \dfrac56\cdot\dfrac22 - \dfrac14\cdot\dfrac33 = \dfrac{5\cdot2}{6\cdot2} - \dfrac{1\cdot3}{4\cdot3} = \dfrac{10}{12} - \dfrac3{12} = \dfrac{10-3}{12} = \dfrac7{12}[/tex]

[tex]\dfrac25 + \dfrac3{10} = \dfrac25\cdot\dfrac22 + \dfrac3{10} = \dfrac{2\cdot2}{5\cdot2} + \dfrac3{10} = \dfrac4{10} + \dfrac3{10} = \dfrac{4+3}{10} = \dfrac7{10}[/tex]

So the simplified expression would be

[tex]\dfrac7{12} x + \dfrac7{10} y[/tex]

how do i do math in division fractions?

Answers

Answer:

The first step to dividing fractions is to find the reciprocal (reverse the numerator and denominator) of the second fraction. Next, multiply the two numerators. Then, multiply the two denominators. Finally, simplify the fractions if needed.

Answer:

Keep change flip!

Step-by-step explanation:

Example 1/2 divided 3/4

We simply keep 1/2 and then we flip the 3/4 which is now 4/3

now we also flip the division sign which its opposite is multiplying now its simply 1/2 x 4/3 and you get 4/6.  Hope this helps please mark brainliest!

help me please please​

Answers

Answer:

17/18

Step-by-step explanation:

To add fractions, you need to have common denominators. (4/9)*(2/2)=8/18.

Now that they have common denominators, you can add 8 and 9 to get 17. So, the answer would be the second one, 17/18.

Answer:

r u just cheating ur way through a whole test lol

Step-by-step explanation:

its B or 17/18

Two parallel lines are cut by a transversal, as shown below. Solve for b. Then explain your reasoning.

Answers

Answer:

b = 14

Step-by-step explanation:

Since both angles are diagonal each other, they are equal to each other.

5b = b + 56

-b      -b           (subtract b from both sides)

4b = 56

4       4            (divide both sides by 4 to solve for b)

 b = 14

Let f(x) = x+2/x+6
f^-1(-6) =

Answers

We can explicitly find the inverse. If [tex]f^{-1}(x)[/tex] is the inverse of [tex]f(x)[/tex], then

[tex]f\left(f^{-1}(x)\right) = \dfrac{f^{-1}(x)+2}{f^{-1}(x)+6} = x[/tex]

Solve for the inverse :

[tex]\dfrac{f^{-1}(x) + 2}{f^{-1}(x) + 6} = x[/tex]

[tex]\dfrac{f^{-1}(x) + 6 - 4}{f^{-1}(x) + 6} = x[/tex]

[tex]1 - \dfrac4{f^{-1}(x) + 6} = x[/tex]

[tex]1 - x = \dfrac4{f^{-1}(x) + 6}[/tex]

[tex]f^{-1}(x) + 6 = \dfrac4{1-x}[/tex]

[tex]\implies f^{-1}(x) = \dfrac4{1-x} - 6[/tex]

Then when x = -6, we have

[tex]f^{-1}(-6) = \dfrac4{1-(-6)} - 6 = \dfrac47-6 = \boxed{-\dfrac{38}7}[/tex]

Alternatively, we can first solve for x such that [tex]f(x) = -6[/tex]. Then taking the inverse of both sides, [tex]x = f^{-1}(-6)[/tex]. (The difference in this method is that we don't compute the inverse for all x.)

We have

[tex]\dfrac{x+2}{x+6} = -6[/tex]

[tex]x + 2 = -6 (x + 6)[/tex]

[tex]x + 2 = -6x - 36[/tex]

[tex]7x = -38[/tex]

[tex]\implies x = \boxed{-\dfrac{38}7}[/tex]

A rectangular swimming pool is 4 ft deep. One side of the pool is 4.5 times longer than the other. The amount of water needed to fill the swimming pool is 1800 cubic feet.
Find the dimensions of the pool.

Answers

Answer:

19 x 23.5 x 4

Step-by-step explanation:

4 * x * (x + 4.5) =1800

Divide both sides by 4

x * (x + 4.5) = 450

Use distributive property

x^2 + 4.5x = 450

Move all terms to one side

x^2 + 4.5x - 450 = 0

Use quadratic formula to solve   a = 1, b = 4.5, c = -450

-4.5 +- [tex]\sqrt{4.5^2 - 4 * 1 * -450}[/tex]/2

=-4.5 + - [tex]\sqrt{1820.25}[/tex] / 2

= -4.5 +- 42.664 / 2

=19.08 and -23.582. You can't have a negative length, so it is 19.08, or 19

19 x 23.5 x 4

20x^5 y^3 + 8x^6 y^3 - 4x^5 y^2
———————————————
4x^5 y^2

Answers

Answer:

1) 4x^{5} y^{2} (5y+2xy-1)

2) Implied to have no solution based on given context.

Step-by-step explanation:

Problem 1:

1) Find the Greatest Common Factor (GCF).

[tex]GCF=4x^{5} y^{2}[/tex]

2) Factor out the GCF. (Write the GCF first. Then, in parentheses, divide each term by the GCF.)

[tex]4x^{5}y^{2} (\frac{20x^{5} y^{3} }{4x^{5}y^{2} } +\frac{8x^{6}y^{3} }{4x^{5} y^{2} } +\frac{-4x^{5} y^{2} }{4x^{5} y^{2} } )[/tex]

3) Simplify each term in parentheses.

[tex]4x^{5} y^{2} (5y+2xy-1)[/tex]

Problem 2:

From the way the problem is given, there is no solution.

Which of the following cannot be used to prove that two triangles are congruent?

A.AAA
B.ASA
C.SSS
D.HL

Answers

Answer:

A

Step-by-step explanation:

:)

hope it helps

Help help help help

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Answer:

-1

Step-by-step explanation:

Answer asap! Need help before I go to sleep.

Answers

Answer:

Step-by-step explanation:

Parallel lines have identical slopes

4x - 7y = 9

7y = 4x - 9

y = (4/7)x - 9/7

so the parallel line has form

y = (4/7)x + b

plug in the point on the line

3 = (4/7)7 + b

b = -1

y = (4/7)x - 1

As you did not tell us where you live and what time you intend to go to bed, we have NO way of knowing your actual deadline

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