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3 years ago

If the population of a town grew 15% up to 76,894, what was the population lest year?

1 answer:

4 0

Let's first find the equation to find what the population went up to. X, will be the population of last year.
1.15x=76,894
Now, we need x by itself, so we need to divide both sides by 1.15.
76,894÷1.15≈66,864
There are decimals, but for this problem, hae .3478 of a person would not fit.
We can check our answer.
66,864×.15=10,029.6
10,029.6+66,864=76,893.6 (rounds up to 76,864)
So the population of the town last year was about 66,864 (66,864.3478) people.

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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

Λ represents the average rate, and the expected number of events in a given time frame for the ____________ distribution.

enot [183]

Answer:

The correct answer is:

Poisson (A.)

Step-by-step explanation:

A Poisson distribution is used to model the number of events occurring within a given time interval, when the average number of times that the event occurs within the time interval is given.

Lambda ( λ ) is a rate parameter in Poisson's distribution, and it is used to represent "event/time", and it simply represents <em>the expected number of events in the interval.</em>

6 0

3 years ago

Is the square root of any positive number irrational

ser-zykov [4K]

No because if it is the square root of 100, then it is rational, hope this helps

5 0

3 years ago

In the 2017 fiscal year, the state of Alaska received $8.2 billion In revenues and had $7.2 billion in expenditures. What percen

konstantin123 [22]

To figure this out you can do 7.2/8.2, because you are trying to figure out how much of the total was used, and percentages would not be more than 100%. Doing this you would get ~.878. To convert this to a percent, you would just multiply it by 100, which would give you 87.8%. The question states to round to the nearest whole percent, leaving you with 88%. This means that 88% of the revenue was spent.

Hope that helped, don't be shy to comment on this if you have any questions about my explanation :)

8 0

2 years ago

Y=-155. Put in a table of 3 rows.

Alja [10]

Answer:

51.6666666667

Step-by-step explanation:

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3 years ago