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3 years ago

15

Multiple representations: bargain DVD's cost $5 each at mega movie graph the proportional relationship that gives the cost y in

dollars of buying x bargain DVD's

1 answer:

krok68 [10]3 years ago

8 0

Answer:

Step-by-step explanation:

With this being a proportional relationship, the y-intercept MUST be 0.

Thus, the relationship has the form y = C(x) = ($5/movie)x, where x is the number of movies purchased.

To graph this, first plot a dark dot at (0, 0). Then, starting at (0, 0), move your pencil point 1 unit to the right and from this new position 5 units up. Plot a dark dot at (1, 5). Now draw a straight line through (0, 0) to the right through (1, 5).

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wolverine [178]

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Dafna1 [17]

Answer:

3x+18

Step-by-step explanation:

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3 years ago

Keith had 694 green,yellow and blue marbles.He had 3 times as many blue marbles as yellow marbles. there were 90fewer green than

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336 blue marbles

Step-by-step explanation:

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3 years ago

I need help with this math question

Vitek1552 [10]

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4 years ago

A flat circular plate has the shape of the region x2 + y2≤1. The plate, including the boundary where x2 + y2 = 1, is heated such

olganol [36]

$T(x,y)=x^2+2y^2-x$
$\implies\nabla T(x,y)=(T_x,T_y)=(2x-1,4y)$

Setting both partial derivatives to 0 gives a single critical point at $(x,y)=\left(\dfrac12,0\right)$ , which does fall inside the unit disk.

At this point, the value of the derivative of the Hessian matrix is

$|H|=\begin{vmatrix}T_{xx}&T_{xy}\\T_{yx}&T_{yy}\end{vmatrix}=\begin{vmatrix}2&0\\0&4\end{vmatrix}=8>0$

while the value of the second-order partial derivative with respect to $x$ is

$T_{xx}\bigg|_{(x,y)=(1/2,0)}=2>0$

This means the critical point is the site of a local minimum, so this is the coldest point on the plate with a temperature of $T\left(\dfrac12,0\right)=-\dfrac14$ .

The hottest point on the plate must then be found on the boundary. Let $x=\cos\theta$ and $y=\sin\theta$ , so that

$T(x,y)=T(\theta)=\cos^2\theta+2\sin^2\theta-\cos\theta$
$T(\theta)=\dfrac32-\cos\theta-\dfrac12\cos2\theta$

Then the boundary of the plate (the circle $x^2+y^2=1$ ) is a function of a single variable $\theta$ considered over $\theta\in[0,2\pi)$ . Differentiating once gives

$T'(\theta)=\sin\theta+\sin2\theta=0$
$\implies\theta=0,\theta=\dfrac{2\pi}3,\theta=\pi,\theta=\dfrac{4\pi}3$

You'll find that $T(\theta)$ attains three extrema on the interval $(0,2\pi)$ , with relative maxima at $\theta=\dfrac{2\pi}3$ and $\theta=\dfrac{4\pi}3$ and a relative minimum at $\theta=\pi$ (and $\theta=0$ , if you want to include that).

We already found our minimum on the inside of our plate - which you can verify to have a lower temperature than at the points given by $T(\theta)$ - and we find two maxima at $\theta=\dfrac{2\pi}3$ and $\theta=\dfrac{4\pi}3$ , each giving a maximum temperature of $T=\dfrac94$ .

Converting back to Cartesian coordinates, these points correspond to the points $\left(-\dfrac12,\pm\dfrac{\sqrt3}2\right)$ .

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4 years ago