What is the solution set for the following equation? 3x^2+11x+10=0

Determine the values of the constants r and s such that i(x, y) = x rys is an integrating factor for the given differential equa

garri49 [273]

$\underbrace{y(7xy^2+6)}_{M(x,y)}\,\mathrm dx+\underbrace{x(xy^2-1)}_{N(x,y)}\,\mathrm dy=0$

For the ODE to be exact, we require that $M_y=N_x$ , which we'll verify is not the case here.

$M_y=21xy^2+6$
$N_x=2xy^2-1$

So we distribute an integrating factor $i(x,y)$ across both sides of the ODE to get

$iM\,\mathrm dx+iN\,\mathrm dy=0$

Now for the ODE to be exact, we require $(iM)_y=(iN)_x$ , which in turn means

$i_yM+iM_y=i_xN+iN_x\implies i(M_y-N_x)=i_xN-i_yM$

Suppose $i(x,y)=x^ry^s$ . Then substituting everything into the PDE above, we have

$x^ry^s(19xy^2+7)=rx^{r-1}y^s(x^2y^2-x)-sx^ry^{s-1}(7xy^3+6y)$
$19x^{r+1}y^{s+2}+7x^ry^s=rx^{r+1}y^{s+2}-rx^ry^s-7sx^{r+1}y^{s+2}-6sx^ry^s$
$19x^{r+1}y^{s+2}+7x^ry^s=(r-7s)x^{r+1}y^{s+2}-(r+6s)x^ry^s$
$\implies\begin{cases}r-7s=19\\r+6s=-7\end{cases}\implies r=5,s=-2$

so that our integrating factor is $i(x,y)=x^5y^{-2}$ . Our ODE is now

$(7x^6y+6x^5y^{-1})\,\mathrm dx+(x^7-x^6y^{-2})\,\mathrm dy=0$

Renaming $M(x,y)$ and $N(x,y)$ to our current coefficients, we end up with partial derivatives

$M_y=7x^6-6x^5y^{-2}$
$N_x=7x^6-6x^5y^{-2}$

as desired, so our new ODE is indeed exact.

Next, we're looking for a solution of the form $\Psi(x,y)=C$ . By the chain rule, we have

$\Psi_x=7x^6y+6x^5y^{-1}\implies\Psi=x^7y+x^6y^{-1}+f(y)$

Differentiating with respect to $y$ yields

$\Psi_y=x^7-x^6y^{-2}=x^7-x^6y^{-2}+\dfrac{\mathrm df}{\mathrm dy}$
$\implies\dfrac{\mathrm df}{\mathrm dy}=0\implies f(y)=C$

Thus the solution to the ODE is

$\Psi(x,y)=x^7y+x^6y^{-1}=C$

4 0

3 years ago

Solve –3 + c = –8.<br> A. -5 B. 11 C. 5 D.-11

sergey [27]

Answer:

The answer is A. -5

Step-by-step explanation:

Write out the equation:

-3 + c = -8 Add 3 on both sides to isolate the varible on one side

c = -5 -8 plus 3 is -5

You must isolate the variable in order to solve equations with variables.

Isolating variable is basically when you divide, multiply, add, or subtract to put a variable on <u><em>ONLY </em></u>one side of the equation.

<h3><u><em>Please rate this and please give brainliest. Thanks!!! </em></u></h3><h3><u><em>Appreciate it! : ) </em></u></h3><h3><u><em>And always, </em></u></h3><h3><u><em>SIMPLIFY BANANAS : )</em></u></h3>

6 0

3 years ago

I need someone to help me

Harlamova29_29 [7]

the second one 6,6,6 it is a square all the others seem like a triangle

8 0

3 years ago

The function f(x) = 1.50x + 12.50 relates how much kelsey pays for digital service, f(x), to the number of movies, x, she stream

Brums [2.3K]

f(18) = 39.50

This gives the monthly cost Kelsey will pay if she streams 18 movies in a month

Step-by-step explanation:

Given function is:

$f(x) = 1.50x+12.50$

Here x is the number of movies

so for f(18), this means that the total number of movies will be 18

Solving

$f(18) = 1.50(18)+12.50\\f(18) = 27+12.50\\f(18) = 39.50$

Hence,

f(18) = 39.50

This gives the monthly cost Kelsey will pay if she streams 18 movies in a month

Keywords: functions, Domain,range

Learn more about functions at:

#LearnwithBrainly

6 0

3 years ago

Johnny took the math test and got 20 out of 25 qustions correct; what grade did Johnny make on the test?

meriva

Answer:

B: 80%

Step-by-step explanation:

:)

5 0

3 years ago

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