Mary biked 4 1/5 miles today, and Mike biked 3 2/3 How many times the

Marine biologists have determined that when a shark detectsthe presence of blood in the water, it will swim in the directionin w

siniylev [52]

Solution :

a). The level curves of the function :

$C(x,y) = e^{-(x^2+2y^2)/10^4}$

are actually the curves

$e^{-(x^2+2y^2)/10^4}=k$

where k is a positive constant.

The equation is equivalent to

$x^2+2y^2=K$

$\Rightarrow \frac{x^2}{(\sqrt K)^2}+\frac{y^2}{(\sqrt {K/2})^2}=1, \text{ where}\ K = -10^4 \ln k$

which is a family of ellipses.

We sketch the level curves for K =1,2,3 and 4.

If the shark always swim in the direction of maximum increase of blood concentration, its direction at any point would coincide with the gradient vector.

Then we know the shark's path is perpendicular to the level curves it intersects.

b). We have :

$\triangledown C= \frac{\partial C}{\partial x}i+\frac{\partial C}{\partial y}j$

$\Rightarrow \triangledown C =-\frac{2}{10^4}e^{-(x^2+2y^2)/10^4}(xi+2yj),$ and

$\triangledown C$ points in the direction of most rapid increase in concentration, which means $\triangledown C$ is tangent to the most rapid increase curve.

$r(t)=x(t)i+y(t)j$ is a parametrization of the most $\text{rapid increase curve}$ , then

$\frac{dx}{dt}=\frac{dx}{dt}i+\frac{dy}{dt}j$ is a tangent to the curve.

So then we have that $\frac{dr}{dt}=\lambda \triangledown C$

$\Rightarrow \frac{dx}{dt}=-\frac{2\lambda x}{10^4}e^{-(x^2+2y^2)/10^4}, \frac{dy}{dt}=-\frac{4\lambda y}{10^4}e^{-(x^2+2y^2)/10^4}$

∴ $\frac{dy}{dx}=\frac{dy/dt}{dx/dt}=\frac{2y}{x}$

Using separation of variables,

$\frac{dy}{y}=2\frac{dx}{x}$

$\int\frac{dy}{y}=2\int \frac{dx}{x}$

$\ln y=2 \ln x$

⇒ y = kx^2 for some constant k

but we know that $y(x_0)=y_0$

$\Rightarrow kx_0^2=y_0$

$\Rightarrow k =\frac{y_0}{x_0^2}$

∴ The path of the shark will follow is along the parabola

$y=\frac{y_0}{x_0^2}x^2$

$y=y_0\left(\frac{x}{x_0}\right)^2$

7 0

2 years ago

How many zeroes are in the product of 40 x 107?

N76 [4]

Answer:

There's one 0.

Step-by-step explanation:

Because I multiplied it and there's only one 0.

4 0

2 years ago

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Is the relationship shown by the data linear? How can you tell if it is or is not? If so, model the data with an equation.

Marat540 [252]

Answer:

linear and y = 2x + 19

Step-by-step explanation:

the x- values increment by 2 and the values of y increment by 4

This indicates a linear relationship exists in the form

y = mx + c ( m is the slope and c the y-intercept )

m = $\frac{rise}{run}$ = $\frac{4}{2}$ = 2

y = 2x + c ← is the partial equation

to find c use any ordered pair from the table

using (- 5, 9 ), then

9 = - 10 + c ⇒ c = 9 + 10 = 19

y = 2x + 19 ← linear equation

As a check

x = - 7 : y = - 14 + 19 = 5 ← correct value of y

x = - 5 : y = - 10 + 19 = 9 ← correct value of y

x = - 3 : y = - 6 + 19 = 13 ← correct value of y

x = - 1 : y = - 2 + 19 = 17 ← correct value of y

4 0

3 years ago

Consider the steps for determining the quotient of 12/x-4 / 4/x-4

Ierofanga [76]

Answer:

Quotient = 3

Step-by-step explanation:

We need to solve the given expression :

$\dfrac{\dfrac{12}{x-4}}{\dfrac{4}{x-4}}$

It can be done as follows :

As, $\dfrac{\dfrac{a}{b}}{\dfrac{c}{d}}=\dfrac{a}{b}\times \dfrac{d}{c}$

So,

$\dfrac{\dfrac{12}{x-4}}{\dfrac{4}{x-4}}=\dfrac{12}{x-4}\times \dfrac{x-4}{4}\\\\=\dfrac{12}{4}\\\\=3$

Hence, the required quotient is 3.

5 0

3 years ago

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In a sale, a clothes shop reduces its prices by 40%

bazaltina [42]

The original price of the shirt is 22
The price was reduced by 40% = 22*40/100 = 8.8
The price after sale = 22.0 - 8.8 = 13.2

4 0

3 years ago