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2 years ago

Help fast as you can worth 7 points

Mathematics

2 answers:

attashe74 [19]2 years ago

6 0

Answer:

Step-by-step explanation:

Klio2033 [76]2 years ago

6 0

Answer: B

Step-by-step explanation: you have to multiply the 4 and 2

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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

In 1992, the countries Chad and Denmark each had population of about 5.2 million. However,

irinina [24]

9514 1404 393

Answer:

5,339,479

Step-by-step explanation:

The populations in millions of the different countries can be represented by the equations ...

c = 5.2(1.025^t)

d = 5.2(1.001^t)

We want to find d when c = 10. Solving for t when c=10, we have ...

10 = 5.2(1.025^t)

10/5.2 = 1.025^t

log(10/5.2) = t×log(1.025)

t = log(10/5.2)/log(1.025)

Then the value of d for that value of t is ...

d = 5.2(1.001^(log(10/5.2)/log(1.025)) ≈ 5.3394789

The population of Denmark is about 5,339,479 when the population of Chad is 10 million.

_____

If we round the number of years to 26.5 before computing the population of Denmark, we get 5,339,571 -- about 92 more people. Ordinarily, one would not round intermediate results.

3 0

3 years ago

At a warehouse the employees can unload 18 trucks in 6 hours what is the unit rate for unloading trucks

NikAS [45]

18/6

18= the number of trucks
6= the number of hours

18/6= 3 trucks per hour

3 0

3 years ago

What is the formula for finding the area of a regular polygon with perimeter P

klio [65]

Answer:

Option B

Coz perimeter is a capital 'P' and apothem length is small 'a'