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Consider the differential equation x^2 y''-xy'-3y=0. If y1=x3 is one solution use redution of order formula to find a second lin

Anastasy [175]

Suppose $y_2(x)=y_1(x)v(x)$ is another solution. Then

$\begin{cases}y_2=vx^3\\{y_2}'=v'x^3+3vx^2//{y_2}''=v''x^3+6v'x^2+6vx\end{cases}$

Substituting these derivatives into the ODE gives

$x^2(v''x^3+6v'x^2+6vx)-x(v'x^3+3vx^2)-3vx^3=0$

$x^5v''+5x^4v'=0$

Let $u(x)=v'(x)$ , so that

$\begin{cases}u=v'\\u'=v''\end{cases}$

Then the ODE becomes

$x^5u'+5x^4u=0$

and we can condense the left hand side as a derivative of a product,

$\dfrac{\mathrm d}{\mathrm dx}[x^5u]=0$

Integrate both sides with respect to $x$ :

$\displaystyle\int\frac{\mathrm d}{\mathrm dx}[x^5u]\,\mathrm dx=C$

$x^5u=C\implies u=Cx^{-5}$

Solve for $v$ :

$v'=Cx^{-5}\implies v=-\dfrac{C_1}4x^{-4}+C_2$

Solve for $y_2$ :

$\dfrac{y_2}{x^3}=-\dfrac{C_1}4x^{-4}+C_2\implies y_2=C_2x^3-\dfrac{C_1}{4x}$

So another linearly independent solution is $y_2=\dfrac1x$ .

3 0

2 years ago

(Will give Brainliest/5 Stars if correct answer)

tensa zangetsu [6.8K]

Answer: Choice D)
The angle between the two vectors is approximately 71.6 degrees

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Work Shown:

Each time I write the word "dot" I mean "dot product".

|u| = length of vector u
|u| = sqrt(u dot u)
|u| = sqrt(<8,4> dot <8,4>)
|u| = sqrt(8*8 + 4*4)
|u| = sqrt(64 + 16)
|u| = sqrt(80)
|u| = sqrt(16*5)
|u| = sqrt(16)*sqrt(5)
|u| = 4*sqrt(5)

-----------------------

|v| = length of vector v
|v| = sqrt(v dot v)
|v| = sqrt(<9,-9> dot <9,-9>)
|v| = sqrt(9*9 + (-9)*(-9))
|v| = sqrt(81+81)
|v| = sqrt(2*81)
|v| = sqrt(2)*sqrt(81)
|v| = sqrt(2)*9
|v| = 9*sqrt(2)

-----------------------

u dot v = <8,4> dot <9,-9>
u dot v = 8*9 + 4*(-9)
u dot v = 72-36
u dot v = 36

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cos(theta) = (u dot v)/(|u|*|v|)
cos(theta) = (36)/(4*sqrt(5)*9*sqrt(2))
cos(theta) = (36)/(36*sqrt(10))
cos(theta) = 1/(sqrt(10))
cos(theta) = sqrt(10)/10
theta = arccos(sqrt(10)/10)
theta = 71.56505
which rounds to 71.6 when rounding to one decimal place (nearest tenth)

That's why the approximate answer is roughly 71.6 degrees

7 0

2 years ago

Please help will mark you as brainliest

zheka24 [161]

Answer:

mark me as brainliest first

Step-by-step explanation:

and I will answer it and the comments

it's so easy though I can answer that

but.. mark this as brainliest first

7 0

2 years ago

Read 2 more answers

Angelo earns $2,080 each month. His total deductions are 30% of his pay. How much is deducted from his pay each month

Olenka [21]

624 is how much is deducted from his pay every month

7 0

2 years ago

Read 2 more answers

How do you find the whole from a percent?

mr Goodwill [35]

N x 100 = n%

An example:
<span>12 is 20% of 60. In order to get 12 percent of 60, all you need to do is to divide 12 with 60. To get the percent means to get the parts of 100. To get it in the form of percent, just multiply the quotient by 100. 12/60=.2 x 100 = 20% .</span>

7 0

3 years ago

Read 2 more answers