Ask question

Ask question

All categories

alexandr402 [8]

2 years ago

15

Kevin is starting a saltwater aquarium with 36 fish. He wants to start with 11 times as many damselfish as clown fish. How many

of each fish will Kevin buy?

1 answer:

meriva2 years ago

3 0

33 damselfish, 3 clownfish

You might be interested in

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

2 years ago

Taiga wants to make a circular loop that she can twirl around her body for exercise. He will use a tube that is 2.5 meters long.

Travka [436]

Answer: 0.796 meters

Step-by-step explanation:

Circumference of circle = $2\pi r$ , where r=radius

Here, Circumference of loop = 2.5 meters

i.e. $2\pi r=2.5$

$\Rightarrow\ r=\dfrac{2.5}{2\pi}$

$\Rightarrow\ r=\dfrac{2.5}{2\times\dfrac{22}{7}}\\\\\Rightarrow\ r=\dfrac{2.5\times7}{2\times22}\\\\\Righttarrow\ r=0.398\ m$

Diameter = 2r = 2(0.398) = 0.796 meters

Hence, The diameter of Taiga's exercise hoop = 0.796 meters

7 0

3 years ago

Which is the value of x

vodka [1.7K]

16.5 is what I got for x you add them up and equal them to 180 because its a straight line

5 0

3 years ago

Read 2 more answers

One cold night the temperature was 0 degrees at 8 p.m. The temperature dropped at a constant rate from 8 p.m. to midnight. At mi

aliina [53]

Answer:

- 4.2 degrees

Step-by-step explanation:

If the drop was from temp 0 at 8 pm to temp -16.8 at midnight (4 hours later)

then,the drop is given by the rate: -16.8/4 = - 4.2 degrees per hour

Therefore, at 9 pm the temperature was:

0 degrees - 4.2 degrees = - 4.2 degrees

5 0

2 years ago

Read 2 more answers

Pls help asap!!!! tysm guys!!

Delvig [45]

Answer:

C. 256 in2

Step-by-step explanation:

8 0

2 years ago

Read 2 more answers