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o-na [289]
3 years ago
13

What is the common ratio of 9, 81, 729. -6561

Mathematics
1 answer:
Gekata [30.6K]3 years ago
6 0

Given:

Consider the given sequence is 9, 81, 729, 6561.

To find:

The common ratio.

Solution:

We have,

9, 81, 729, 6561

Here,

First term = 9

Second term = 81

Divide the second term by first term to get the common ratio.

r=\dfrac{81}{9}

r=9

Similarly,

\dfrac{81}{9}=\dfrac{729}{81}=\dfrac{6561}{729}=9=r

Therefore, the common ratio is 9.

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Solve the initial value problem where y′′+4y′−21 y=0, y(1)=1, y′(1)=0 . Use t as the independent variable.
igor_vitrenko [27]

Answer:

y = \frac{7}{10} e^{3(t - 1)} + \frac{3}{10}e^{-7(t - 1)}

Step-by-step explanation:

y′′ + 4y′ − 21y = 0

The auxiliary equation is given by

m² + 4m - 21 = 0

We solve this using the quadratic formula. So

m = \frac{-4 +/- \sqrt{4^{2} - 4 X 1 X (-21))} }{2 X 1}\\ = \frac{-4 +/- \sqrt{16 + 84} }{2}\\= \frac{-4 +/- \sqrt{100} }{2}\\= \frac{-4 +/- 10 }{2}\\= -2 +/- 5\\= -2 + 5 or -2 -5\\= 3 or -7

So, the solution of the equation is

y = Ae^{m_{1} t} + Be^{m_{2} t}

where m₁ = 3 and m₂ = -7.

So,

y = Ae^{3t} + Be^{-7t}

Also,

y' = 3Ae^{3t} - 7e^{-7t}

Since y(1) = 1 and y'(1) = 0, we substitute them into the equations above. So,

y(1) = Ae^{3X1} + Be^{-7X1}\\1 = Ae^{3} + Be^{-7}\\Ae^{3} + Be^{-7} = 1      (1)

y'(1) = 3Ae^{3X1} - 7Be^{-7X1}\\0 = 3Ae^{3} - 7Be^{-7}\\3Ae^{3} - 7Be^{-7} = 0 \\3Ae^{3} = 7Be^{-7}\\A = \frac{7}{3} Be^{-10}

Substituting A into (1) above, we have

\frac{7}{3}B e^{-10}e^{3} + Be^{-7} = 1      \\\frac{7}{3}B e^{-7} + Be^{-7} = 1\\\frac{10}{3}B e^{-7} = 1\\B = \frac{3}{10} e^{7}

Substituting B into A, we have

A = \frac{7}{3} \frac{3}{10} e^{7}e^{-10}\\A = \frac{7}{10} e^{-3}

Substituting A and B into y, we have

y = Ae^{3t} + Be^{-7t}\\y = \frac{7}{10} e^{-3}e^{3t} + \frac{3}{10} e^{7}e^{-7t}\\y = \frac{7}{10} e^{3(t - 1)} + \frac{3}{10}e^{-7(t - 1)}

So the solution to the differential equation is

y = \frac{7}{10} e^{3(t - 1)} + \frac{3}{10}e^{-7(t - 1)}

6 0
3 years ago
Need an answer to both please
ANTONII [103]

Plz mark me the braniliest

Answer:

1st answer: 52 serves

2nd answer: $8.40

Step-by-step explanation:

1st: 80 times 65 equals 5,200 divided by 100 equals 52

2nd: 42 times 0.20 equals 8.4 or 8.40

6 0
3 years ago
An article bought for $125 was sold for $175. The percentage profit was
777dan777 [17]

Answer:

Step-by-step explanation:

28.57% profit.

You're welcome.

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6 0
2 years ago
I need help finding the lateral area and surface area of this cylinder but I have to leave π in my answer. Can anyone help?
Pani-rosa [81]
The lateral surface of a cylinder can be found with the equation 

A = 2 π r h          Substitute in your values.
A = 2 π (11) (7)   Multiply 11 and 7.
A = 2 π (77)        Multiply 77 and 2.
A = 154π            Don't simplify anymore so you can keep pi in the answer.

The surface are uses the equation
 
A = 2 π r h + 2 π r²               Substitute in your values.
A = 2 π (11) (7) + 2 π (11)²   Simplify and multiply your terms.
A = 2 π (77) + 2 π (11)²
A = 154 π + 2 π (11)²
A = 154 π + 2 π (121)
A = 154 π + 242 π                Since both terms are in terms of pi, you can                                                 combine them.
A = 396π                              Stop simplifying to leave the answer in terms                                               of pi.



8 0
3 years ago
If i= -1, what is the value of i3?<br>-1<br>i <br>1<br>-i ​
mario62 [17]

Answer:

Step-by-step explanation:

-1

3 0
3 years ago
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